The World Food Programme said Friday it had brought desperately-needed supplies into war-ravaged Sudan's Darfur region for the first time in months, but warned that hunger there could worsen.

Fighting in Sudan broke out on April 15 last year between forces loyal to the army chief Abdel Fattah al-Burhan and to Mohamed Hamdan Daglo, his former deputy and commander of the paramilitary Rapid Support Forces.

The conflict has killed thousands and has sparked a humanitarian disaster.

Around 25 million people -- more than half the population -- need aid, including nearly 18 million who face acute food insecurity, according to the UN.

On Friday, the WFP said two aid convoys crossed into the western region from neighboring Chad in late March, carrying food and nutrition assistance for around 250,000 people facing acute hunger.

Food distribution is now underway in West and Central Darfur, WFP's Sudan spokeswoman Leni Kinzli said Friday.

The deliveries were the first WFP cross-border aid convoys to reach Darfur following lengthy negotiations to reopen humanitarian corridors from Chad after permission was revoked in February by authorities loyal to the Sudanese army.

"We are extremely concerned that unless the people of Sudan receive a constant flow of aid via all possible humanitarian corridors -- from neighboring countries and across battle lines -- the country's hunger catastrophe will only worsen," Kinzli told a press briefing in Geneva, via video-link from Nairobi.

"The temporary halt of the humanitarian corridor from Chad as well as ongoing fighting, lengthy clearance processes for humanitarian cargo, bureaucratic impediments, and security threats have made it impossible for humanitarians to operate at the scale needed to meet the hunger needs in Sudan," Kinzli said.

 Hunger 'will only increase' 

 The cereals harvest in Darfur was 78 percent below the five-year average, while levels of hunger in West Darfur were alarming, she said.

"Hunger in Sudan will only increase as the lean season starts in just a few weeks. Our greatest fear is that we will see unprecedented levels of starvation and malnutrition sweep across Sudan this lean season -- and that the Darfur region will be particularly hard-hit."

Kinzli said the route from Chad was "vital if the humanitarian community stands a chance of preventing widespread starvation" in West Darfur.

A separate convoy of trucks reached North Darfur from Port Sudan on the Red Sea in late March, which WFP said was the first aid delivery to be transported across conflict lines in six months.

World Health Organization spokeswoman Margaret Harris told the briefing that humanitarian needs in Sudan were at record highs.

"Essentially, the health situation is disastrous... This is an ongoing health catastrophe," she said.