KHARTOUM, SUDAN — A surge of truck hijackings threatens to cut off food rations for more than 2 million people in Darfur, the World Food Program said yesterday, after 22 of its vehicles were attacked and stolen this month alone.

With 18 drivers still missing, the U.N. agency said its main contracting companies refuse to send more food convoys into Darfur.

“If the situation continues, we’ll be forced to cut rations in parts of Darfur by mid-February,” the head of WFP operations in Sudan, Kenro Oshidari, said in a statement.

The increase in violence comes barely three weeks after the United nations took over peacekeeping in the remote region of western Sudan where 2.5 million people have been chased into refugee camps by five years of war.

Five separate attacks targeted aid workers throughout Darfur just on Tuesday, officials said.

Among those were ambushes of two WFP convoys in West Darfur and the detention of five WFP staff when their cars were stolen near the North Darfur state capital of El Fasher.

“They’ve now been released, but it was pretty traumatic,” the WFP spokeswoman in Sudan, Emilia Casella, said.

A vehicle from the U.N. security services was also attacked near the West Darfur capital of El Geneina, while an aid group’s car was attacked inside the capital, which is under Khartoum government control.

The agency said it didn’t know who was behind the latest attacks, which it blamed on “bandits.”

Top U.N. aid officials met with the Sudanese government yesterday to extend by a year the agreement that allows international aid groups to work in Sudan, but the meeting didn’t address the increased hijackings.

Over the past year, WFP has been feeding between 2 million and 3.2 million people in Darfur. It plans to distribute some $500 million worth of food in the region during 2008.

The food convoys to Darfur form the world’s longest humanitarian route, with nearly 1,864 miles to cross between the nearest port on the Red Sea to the desert town of El Geneina, near the border with Chad.

Nearly twice as many WFP trucks have been hijacked this month than in the previous four months combined, and the United Nations said seven humanitarian vehicles have also been stolen so far.

Some 369 tons of food were looted in the latest attacks, and the lack of trucks means deliveries will be cut by half.

The escalation came as the United nations launched a new peacekeeping mission to try to quell the chaos in Darfur, where more than 200,000 people have died since early 2003, when ethnic African groups rebelled against the Arab-dominated central government and accused it of discrimination.

The U.N. mission had a supply convoy attacked by the Sudanese army days after taking over from the previous African Union force on January 1.

The new mission is meant to grow to 26,000 peacekeepers and police officers, but less than half have reached Darfur.