Ukrainian President Volodymyr Zelensky said Monday he doesn't believe it is the right time for elections as debate intensifies on holding a vote in 2024 while the country fights against Russia's invasion.

All elections including the presidential vote set to take place next spring are technically cancelled under martial law that has been in effect since the conflict began last year.

"We must decide that now is the time of defence, the time of battle, on which the fate of the state and people depends," Zelensky said in his daily address.

He said it was a time for the country to be united, not divided, adding: "I believe that now is not the (right) time for elections."

The frontline between the warring sides has remained mostly static for almost a year despite a much-touted Ukrainian counter-offensive, with Russian forces entrenched in southern and eastern Ukraine.

Officials from the United States and Europe -- Kyiv's key allies -- are reported to have suggested holding negotiations to end the grinding 20-month-old conflict.

But Zelensky has fiercely denied that Ukraine's counter-offensive has hit a stalemate, or that Western countries were leaning on Kyiv to enter talks.

The United States and other supporters have publicly maintained they are ready to back Kyiv with military and financial aid for as long as it takes to defeat Russia.

Global attention has turned to the Middle East since the October 7 Hamas attack on Israel -- and Zelensky has come under increasing pressure.

The president, who was elected in 2019, said in September that he was ready to hold national elections next year if necessary, and was in favour of allowing international observers.

Voting could be logistically difficult due to the large number of Ukrainians abroad and soldiers fighting on the front.

Zelensky's approval rating skyrocketed after the war began, but the country's political landscape has been fractious despite the unifying force of the war.

Former presidential aide Oleksiy Arestovych has announced that he would run against his former boss, after criticising Zelensky over the slow pace of the counter-offensive.

- Arts museum hit -

Russian strikes overnight in the southern Ukrainian region of Odesa left eight people wounded and damaged a historic art museum, Ukrainian officials said, in the latest barrage of drones and missiles.

Three more were injured in a Russian shelling attack on the southern city of Kherson on Monday, as Kyiv doubled down on its warnings that Russia was planning to pummel Ukraine's energy infrastructure ahead of the winter.

Images released by officials from inside the Odesa Fine Arts Museum showed art ripped from the walls of the 19th-century building and windows blown out by the aerial bombardment.

UNESCO said it "strongly condemns the attack" and that "cultural sites must be protected".

On Monday, Zelensky said that Ukrainian forces had successfully destroyed a major Russian ship in the Kerch shipyard in annexed Crimea.

- Advisor killed -

Ukraine has been fighting an uphill battle against systemic corruption as part of reforms urged by the West for membership in institutions like the European Union.

Ukrainian prosecutors said Monday they had formally notified two senior defence officials that they are suspects in a large-scale fraud case involving the purchase of military uniforms.

Also on Monday, a close advisor to the commander-in-chief of the Ukrainian army, General Valery Zaluzhny, was killed when a grenade among his birthday gifts exploded, officials said.

"My assistant and close friend, Major Gennadiy Chastiakov, was killed... on his birthday," Zaluzhny said, adding that police had identified a fellow soldier who gave the fatal gift.

Chastiakov was showing his son one of the grenades moments before the explosion, Interior Minister Igor Klymenko said.

"At first, the son took the munition in his hands and began to turn the ring. Then the serviceman took the grenade away from the child and pulled the ring, causing a tragic explosion," Klymenko said.

Grenade kills military adviser on birthday

A close adviser to the commander-in-chief of the Ukrainian army was killed when a grenade among his birthday gifts exploded on Monday, officials said.

"Under tragic circumstances, my assistant and close friend, Major Gennadiy Chastiakov, was killed... on his birthday," General Valery Zaluzhny said on Telegram, saying that an "unknown explosive device detonated in one of his gifts".

Chastiakov was showing his son a box with grenades inside that he had received as a gift, Interior Minister Igor Klymenko said in a statement on Telegram.

"At first, the son took the munition in his hands and began to turn the ring. Then the serviceman took the grenade away from the child and pulled the ring, causing a tragic explosion," Klymenko said.

Police have identified a fellow soldier who gave the fatal gift, he said, and seized two similar grenades.

An investigation is under way.

Chastiakov leaves a wife and four children, Zaluzhny said.

He added that since Russia invaded Ukraine in February 2022, Chastiakov had been "fully devoting his life to the Armed Forces of Ukraine and the fight against Russian aggression".

Attacks targeting Ukrainian leaders have been relatively rare since Moscow invaded, but there have been several attacks on nationalists which Russia has blamed on Ukraine.

In April, a blast from a statuette rigged with explosives killed 40-year-old pro-Kremlin military blogger Vladlen Tatarsky.

The Kremlin said the attack had been orchestrated by Ukraine with the help of supporters of jailed Kremlin critic Alexei Navalny.

But observers said the bombing attack could be used to justify a further crackdown on critics.

And last August, Darya Dugina, the daughter of a prominent ultranationalist intellectual, was killed in a car bombing outside Moscow, which Russia blamed on Ukraine.

Kyiv denied the charges.