WASHINGTON -- The United States on Monday barred most travel by its diplomats in Ivory Coast as the U.S. Embassy in Abidjan reported that mutinous soldiers in the rebel-held town of Bouake were releasing convicts and arming them after an apparent failed coup attempt.

The travel restrictions were imposed as Ivorian troops mounted a brief attack on mutineers in Bouake, the West African country's second-largest city, where some 1,000 foreigners, including 170 schoolchildren, most of them U.S. citizens, are trapped.

"The embassy regrets that due to the ongoing situation in cote D'Ivoire, all non-essential travel (must) be deferred until further notice," the U.S. mission in Abidjan said, using the French name for the country, AFP reported. In a notice to citizens in Ivory Coast made available to AFP in Washington by the State Department, the embassy also urged that travelers avoid using the international airport in Abidjan "due to the possibility of travelers being stranded due to unexpected cancellations of scheduled flights."

It said the atmosphere in Abidjan, where a dusk-to-dawn curfew has been imposed, was "calm but tense" amid reports of sporadic gunfire, though it added that the embassy and the American school there would remain closed on Tuesday. Shortly after the attack by government troops in Bouake, the embassy, citing witness accounts, said rebel troops were driving through the streets of the city in trucks "with mounted rocket grenade launchers or heavy machine guns."

one Bouake resident said the rebels had "released and armed more than 500 prisoners and local youth," according to the notice.

The State Department has already twice -- once on Thursday and again on Sunday -- urged U.S. citizens to postpone any travel to Ivory Coast and on Friday condemned the uprising as a threat to democracy, and the rule of law.

Monday's notice reported that the mainly expatriate Kennedy neighborhood in Bouake was quiet but said the many residents were without power, water and telephone service.

Earlier, the State Department said it was in close touch with France, Ivory Coast's former colonial ruler, about the possible evacuation of about 1,000 foreigners, including the children who attend a boarding school for the families of Christian missionaries, from Bouake.

French troops are now in Ivory Coast's administrative capital, Yamoussoukro, 60 miles (100 kilometers) south of Bouake, preparing for a possible evacuation of foreign nationals from the town.

State Department spokesman Richard Boucher said Washington and Paris were "coordinating closely" about a potential rescue effort, but stressed that U.S. officials were in constant contact with the International Christian Academy in Bouake and that all the students were safe.

Soon after Boucher spoke, Ivorian troops attacked what appeared to be a military training college in Bouake and a U.S. official said an evacuation operation was "likely," but not certain, depending on the situation.

At least 270 people have been killed and more than 300 wounded in the apparently well-coordinated uprising which began on Thursday with rebels attacking government positions in Bouake, the commercial capital of Abidjan and the northern town of Korhogo.

Ivorian President Laurent Gbagbo has said the rebellion was an attempted coup d'etat, but Boucher and other U.S. officials declined to characterize the uprising, calling the situation too "fluid" to judge.