Nairobi, Kenya ? Hundreds of rebels charged into Chad’s capital aboard pickup trucks Saturday, clashing with government troops around the presidential palace in the most forceful attempt yet to oust President Idriss Deby.

Libya’s official news agency, JANA, reported that Chadian rebel leader Mahamat Nouri agreed to a cease-fire Saturday night after speaking to Libyan leader Moammar Gadhafi, who was appointed by the African Union to mediate in the crisis. The report could not be confirmed.

The violence endangered a $300 million global aid operation supporting millions of people in the former French colony and also delayed the deployment of the European Union’s peacekeeping mission to both Chad and neighboring Central African Republic.

The rebels arrived after a three-day push across the desert from the eastern border with Sudan in about 250 pickups with mounted submachine guns.

The rebels gathered outside N’Djamena overnight before 1,000 to 1,500 fighters entered early Saturday and spread through the city, said Col. Thierry Burkhard, a French military spokesman.

Government forces were pushing rebels away from N’Djamena, he said late Saturday. “It appears clear that President Deby succeeded in containing them at his palace and is even in the process of pushing them back,” Burkhard said.

A bomb hit the residence of the Saudi ambassador to Chad, killing the wife and daughter of an embassy staffer taking shelter from the fighting, according to a Saudi Foreign Ministry statement.

Chad’s ambassador in Ethiopia, Cherif Mahamat Zene, told The Associated Press “the situation is under control.

“The head of state is fine in his palace. It’s true that there are some rebels who have entered the city, but to say the city has fallen is false.” Zene said his information came from a telephone call with the defense minister in N’Djamena.

A spokesman for the biggest rebel group told the AP that its forces had surrounded the presidential palace and claimed that government soldiers were defecting.

“Many in the military have rallied with the rebels,” said Mahamat Hassane Boulmaye of the Union of Forces for Democracy and Development. He was reached on a Sudanese mobile telephone number and said he was on Chad’s border with Sudan.

Chad, a French colony until 1960, has been convulsed by civil wars and invasions since independence, and the recent discovery of oil has only increased the intensity of the struggle for power in the largely desert country about three times the size of California.

In April 2006, one Chadian rebel group launched a failed assault on N’Djamena.

The rebel force is believed to be a coalition of three groups, including the biggest led by Nouri, a former diplomat who defected 16 months ago, and a nephew of Deby’s, Timan Erdimi. They long have been fighting to overthrow Deby, whom they accuse of corruption. Deby, himself a soldier, has suffered many defections in the past and morale is low in the army.

The African Union, holding a summit in Ethiopia, said it would not recognize the rebels should they seize power.

The U.S. Embassy urged Americans seeking evacuation to get to the embassy. State Department spokesman Karl Duckworth said the embassy had authorized the departure of nonessential personnel and family members.