GOMA, Congo (AP) — Rebels started to retreat from Congo’s eastern provincial capital on Saturday after an attempt to garner ammunition at the airport failed and their original pullout was postponed, a U.N. official said.

Trucks full of M23 rebels drove along the road that leads out of Goma toward Kibumba, where the rebels are supposed to settle following an agreement reached in Kampala last week with nations bordering Congo. M23 soldiers were cheering as they did a final tour in the city center.

The rebels believed to be backed by Rwanda has defied two earlier ultimatums to leave Goma, raising the possibility they did not intend to leave and giving credence to a U.N. report accusing Rwanda of using the rebels as a proxy to annex territory in the mineral-rich eastern Congo.

The apparent withdrawal of the M23 rebels, however, comes after rebels on Friday attempted to force their way into Goma’s international airport in order to seize arms belonging to the Congolese military which were being safeguarded there.

"An agreement was reached yesterday over the ammunitions issue," said Sy Koumbo, a spokesman for the U.N. mission in Congo. He said that U.N. peacekeepers had control of the airport and blocked the fighters from obtaining the arms.

"We did not give them the ammunition. It seems they are leaving now," Koumbo said.

U.N. peacekeepers were also posted along the road out of Goma.

The eight-month-old M23 rebellion is led by fighters from a now-defunct rebel group, who agreed to lay down their arms on March 23, 2009, in return for being allowed to join the ranks of the Congolese army. M23 takes its name from the date of that accord, and the rebellion began in April, when hundreds of soldiers defected from the military, saying that the terms of the accord had not been respected.

In fact, most analysts believe the origin of the rebellion is a fight over Congo’s vast mineral wealth, a good chunk of which is found in the North Kivu province where Goma is the capital. Starting this spring, the fighters seized a series of small towns and villages in North Kivu, culminating with the capture on Nov. 20 of Goma, a population hub of 1 million and a key, mineral trading post.

The regional bloc representing the nations bordering Congo had issued a Friday deadline for the M23 fighters to retreat from Goma, after the rebels had thumbed their nose at an earlier ultimatum.

M23 rebels began retreating on Tuesday from the other territories they seized.