Congolese rebels said they reached the outskirts of Goma and declared a cease-fire Wednesday to prevent panic in the city, where retreating government soldiers were commandeering cars and firing wildly as people fled in torrents.

Goma's governor, Julien Mpaluku, acknowledged panic was spreading in the eastern provincial capital. He stressed that U.N. peacekeepers were still in charge.

Still, the U.S. embassy said its officials were leaving Goma and urged all American citizens to follow.

Hundreds of foreign aid workers were also trying to evacuate.

Rebel leader Laurent Nkunda has threatened to take Goma despite calls from the U.N. Security Council for him to respect a U.N.-brokered cease-fire signed in January.

U.N. spokesman Madnodje Mounoubai said peacekeepers were at the airport and in other strategic points.

“What we fear is that if General Nkunda takes the town, is that there will be chaos … and maybe even killing on a large scale,” John Holmes, the U.N.'s under-secretary-general for humanitarian affairs, told Britain's Channel 4 News.

Refugees said the Tutsi rebels had already overrun Kibati, a village seven miles north of Goma. About 45,000 people fled the Kibati camp in a matter of hours Wednesday, according to the U.N..

The U.N. says its biggest peacekeeping mission – a 17,000-strong force – is now stretched to the limit and needs more troops quickly.

But hopes for immediate backup from the European Union dimmed. French Foreign Minister Bernard Kouchner said Wednesday that EU had considered sending reinforcements but “a certain number of countries refused.” He offered no further details.

There were also fears the fighting could explode into a conflict that dragged in neighboring African countries.