Mining giant Anglo American on Friday unveiled the world's largest hydrogen-powered truck, a monster weighing in at 220 tonnes, at a platinum mine in northern South Africa.

Billed as the first of a fleet that will replace the firm's diesel-powered trucks, the vehicle uses two-megawatt hydrogen fuel cells to haul up to 290 tonnes of ore.

"What we are launching is not merely an impressive piece of machinery, it is the genesis of an entire ecosystem powered by hydrogen," President Cyril Ramaphosa said.

Comparable in size to a small house, the behemoth was shown off at Mogalakwena mine, about 250 kilometres (150 miles) from Johannesburg.

"This is a gigantic leap for South Africa's hydrogen future economy," Ramaphosa declared.

"This has really been a historic moment. It gives us a clear vision of what the future looks like."

Anglo American said it aims to be carbon neutral by 2040.

It will use solar power to provide the fuel, using the energy to split water into its component atoms of hydrogen and oxygen.

Burning hydrogen releases only water vapour, not heat-trapping carbon dioxide as in the case of fossil fuels.

"Over the next several years, we envisage converting or replacing our current fleet of diesel-powered trucks with this zero-emission haulage system, fuelled with green hydrogen," chief executive Duncan Wanblad said.

"If this pilot is successful, we could remove up to 80 percent of diesel emissions at our open pit mines by rolling this technology across our global fleet."

Last November, rich nations including France, Germany, Britain and the United States pledged at least $8.5 billion and technical assistance to help South Africa switch to a low-carbon economy.

Civilians await renewed rescue bid at besieged Ukraine plant

A UN convoy was to resume evacuations Friday of civilians still holed up inside a besieged Mariupol steelworks, the last pocket of Ukrainian resistance against Russian forces in the port city, but reports of renewed firing cast doubt on a promised truce.

About 200 civilians, including children, are estimated to still be trapped in the Soviet-era tunnels and bunkers beneath the sprawling Azovstal factory, along with a group of Ukrainian soldiers making their last stand.

Russia had earlier announced a daytime ceasefire at the plant for three days, starting Thursday.

But the Ukrainian army says Russian "assault operations" have continued by ground and by air.

Ukraine's Azov battalion, leading the defence at Azovstal, accused Russian forces of firing during an attempt to evacuate people by car.

"During the ceasefire at the Azovstal plant, a car was hit by Russians who used an anti-tank guided weapon," the battalion said on Telegram, saying the vehicle was "moving towards civilians to evacuate them" at the time.

The strike killed one Ukrainian fighter and wounded six others, it said.

Ten weeks into a war that has killed thousands, destroyed cities and uprooted more than 13 million people, defeating the resistance at Azovstal and taking full control of strategically located Mariupol would be a major win for Moscow.

May 9 fears

It would also be a symbolic success as May 9 approaches, the day Russia celebrates the Soviet victory over the Nazis in World War II.

Ukrainian officials believe Moscow is planning a May 9 military parade in Mariupol, possibly with Ukrainian prisoners on display.

The Kremlin Friday however denied plans for Victory Day celebrations in Mariupol, flattened by relentless Russian bombardment.

Moscow-backed separatists in southeastern Ukraine meanwhile said they had taken down traffic signs spelling out the name of Mariupol in Ukrainian and English, and replaced them with Russian ones.

Locals want to see proof that "Russia has come back here forever," said Denis Pushilin, head of Ukraine's breakaway region of Donetsk.

'Hell'

The United Nations had said Thursday a convoy was en route to help civilians escape the "bleak hell" of Azovstal, where food and water are running out and medical care is minimal.

The convoy was expected to arrive sometime Friday, in what would be the third joint evacuation operation with the Red Cross in Mariupol.

Almost 500 civilians were already evacuated from Mariupol and Azovstal in the previous UN-organised rescue missions in recent days, said the head of Ukraine's presidential office, Andriy Yermak.

He said renewed rescue efforts continued and that he would "give the results of this later".

During last weekend's rescues from Mariupol, civilians left in white buses, some taking three days to complete a 230-kilometre (140-mile) journey to Ukraine-controlled Zaporizhzhia, passing through multiple Russian checkpoints.

Azov battalion leader Andriy Biletsky wrote on Telegram Friday that the situation at the plant was critical.

"The shelling does not stop. Every minute of waiting is costing the lives of civilians, soldiers, and the wounded."

Speaking to the Israeli prime minister Thursday, Russian President Vladimir Putin said his army was "ready" to provide safe passage to civilians at Azovstal. But he said the last Ukrainian defenders had to surrender.

Staying 'forever'

Since failing to take Kyiv early on in the war, which began with Moscow's invasion on February 24, Russia has refocused its offensive on the south and east of Ukraine.

Taking full control of Mariupol would allow Moscow to create a land bridge between separatist, pro-Russian regions in the east and the Crimean peninsula, which it annexed in 2014.

Elsewhere, a Ukrainian official said Russian forces had almost encircled Severodonetsk, the easternmost city still held by Kyiv, and are trying to storm it.

Kherson in the south remains the only significant city Russia has managed to capture since the war began.

A senior official from the Russian parliament visiting Kherson Friday said Russia would remain in southern Ukraine "forever".

"There should be no doubt about this. There will be no return to the past," Andrey Turchak said.

Pentagon denial

The United States is among Ukraine's biggest backers, supplying military equipment and munitions worth billions of dollars as well as intelligence and training.

But the White House has sought to limit knowledge of the full extent of its assistance to avoid provoking Russia into a broader conflict beyond Ukraine.

The Pentagon on Friday denied reports that it helped Ukrainian forces sink the Russian warship Moskva in the Black Sea last month in a stunning setback for Moscow's invasion.

Pentagon spokesman John Kirby said the US had "no prior knowledge" of the plan to strike the ship, which sank April 13, leaving a still-unclear number of Russian sailors dead or missing.

Oil embargo row

Ukraine's government has estimated at least $600 billion will be needed to rebuild the country after the war.

Ukraine's Western allies have supported Kyiv with financial and military assistance, and have slapped unprecedented sanctions on Russia.

In what would its toughest move yet, the European Commission has proposed that all 27 EU members gradually ban Russian oil imports.

But Hungarian Prime Minister Viktor Orban, whose country is hugely reliant on Russian oil, said the ban would cross a "red line" for Budapest.

On the diplomatic front, Berlin announced that leaders of the G7 group of industrialised nations would hold video talks with Ukrainian President Volodymyr Zelensky Sunday.

Farmers on front line

The war is expected to have a deep impact on food crops in Ukraine, a country known as Europe's breadbasket.

Ukraine's wheat production is likely to be down by at least a third from last year due to Russia's invasion, according to data analysis firm Kayrros, using satellite imagery.

Some farmers are risking their lives to keep up with the spring planting season, finding themselves ploughing around unexploded ordnance.

"Every day since the start of the war we have been finding and destroying unexploded ammunition," Dmytro Polishchuk, one of the deminers, told AFP before heading into a field in the southwestern village of Grygorivka to destroy an unexploded rocket.

No Harry, Meghan or Andrew on queen's jubilee balcony: palace

Queen Elizabeth's son Prince Andrew, her grandson Harry and his wife Meghan will not join her on the Buckingham Palace balcony for this year's Trooping the Colour, royal officials said on Friday.

Instead, the 96-year-old monarch has decided to limit numbers for the traditional set-piece appearance on her official birthday celebration to working royals only.

"Only those members of the royal family who are currently undertaking official public duties on behalf of the queen" will join her on June 2, a spokesman said.

The decision was taken "after careful consideration", he added.

Speculation had mounted that all three could be at the event, which kicks off four days of public celebrations for the queen's Platinum Jubilee.

Andrew, 62, in March made his first public appearance since settling a US civil claim for sexual assault, and after public outrage at his friendship with convicted sex offender Jeffrey Epstein.

The former Royal Navy helicopter pilot provided his mother, who has been in ill health and had difficulty walking and standing, with a steadying arm at a memorial service to her late husband, Prince Philip.

His prominent role at the televised Westminster Abbey event was seen as a sign that his mother believed he still has a part to play at family occasions.

But his appearance caused controversy and dominated coverage of the memorial service and Friday's announcement may be seen as a sign the palace does not want a repeat.

Andrew has strenuously denied the assault claims and remains stripped of his honorary military titles and charities, giving him no official royal role.

Senior royals

Speculation that Harry would return from his self-imposed exile in California has also increased after he visited his grandmother at her Windsor Castle home last month.

The 37-year-old former British Army captain is the second son of her eldest son and heir Prince Charles, and his first wife, Princess Diana.

He quit royal life in March last year, moving to the United States with his wife Meghan, where both have publicly complained about life in Britain's most famous family.

The couple, who still use their official titles of the Duke and Duchess of Sussex, are now involved in charitable and philanthropic work.

Denying them a place on the balcony will likely be seen as the queen refusing to accept a "half-in, half-out" approach to royal duties.

There was no immediate word on whether all three would be involved in the other public events to mark the queen's record-breaking 70 years on the throne.

But a spokeswoman for Harry and Meghan indicated they would be there with their children Archie, who turned three on Friday, and Lilibet, who was born in June last year and has yet to meet her great-grandmother.

The couple were "excited and honoured to attend the queen's Platinum Jubilee celebrations this June with their children", she added.

The decision means the queen will be joined on the balcony for the end of the military pageant and ceremonial fly-past by senior royals led by Charles and his second wife, Camilla.

Harry's older brother Prince William and his wife Kate will be there, with their children, Prince George, Princess Charlotte and Prince Louis.

The queen's youngest son, Prince Edward, will be accompanied by his wife, Sophie, and their children Louise and James.

Her only daughter, Princess Anne, will also be on the balcony. The queen has allowed her second husband, Tim Laurence, even though he is not a working royal.

The palace spokesman said the queen recognised him as a "frequent attendee and support for the Princess Royal (Anne) on official engagements".

Saudi-led coalition says frees Yemen rebels in peace gesture

The Saudi-led military coalition fighting Yemen's Huthi insurgents said Friday it was freeing a batch of rebel prisoners, part of what it describes as efforts to end the seven-year war.

Last week, the coalition said it would release 163 prisoners it accused of participating in "hostilities" against Saudi Arabia.

The official Saudi Press Agency said on Twitter Friday that process had begun, adding there would be "three stages of air transport of prisoners" to Yemen's Huthi-controlled capital Sanaa and the southern port city of Aden.

It did not say how many prisoners would be let go, but a spokesman for the International Committee of the Red Cross told AFP the organisation was "facilitating the transfer of more than 100 Yemeni former detainees from Saudi Arabia to Yemen".

The spokesman, Basheer Omar, said there would be three ICRC flights from the Saudi city of Abha to Aden.

State media footage purported to show released prisoners, in white robes and holding white roses, aboard an ICRC aircraft and then disembarking in Aden. Their identities could not be independently verified.

The conflict pits Yemen's Saudi-backed government, officially based in Aden, against the Iran-aligned Huthis.

It has killed hundreds of thousands of people and pushed the Arab world's poorest country to the brink of famine.

It has also featured Huthi strikes on neighbouring Saudi Arabia and the United Arab Emirates, another member of the coalition.

But a renewable two-month truce that went into effect in early April has provided a rare respite from violence in much of the country, and has seen oil tankers begin arriving at the rebel-held port of Hodeida, potentially easing fuel shortages in Sanaa and elsewhere.

The truce also involved a deal to resume commercial flights out of Sanaa's airport for the first time in six years and to open main roads leading into the besieged government-held city of Taez —though neither step has been taken so far.

In late March, just before the truce took effect, the Huthis said they had agreed to a prisoner swap that would see 1,400 rebels freed in exchange for 823 pro-government fighters including 16 Saudis and three Sudanese.

The last such swap was in October 2020, when 1,056 prisoners were released on each side, according to the Red Cross.

Huthi media reported on April 23 that the rebels had released 42 prisoners.

The Huthis took over Sanaa in 2014, prompting the Saudi-led military intervention the following year and igniting a war that has caused what the United Nations terms the world's worst humanitarian crisis.