Security concerns deepened in the capital of Central African Republic on Friday after the U.S. ambassador and his diplomatic team were evacuated out of the country by plane overnight amid fears rebels could try to take the capital.

U.S. officials said about 40 people were evacuated on an U.S. Air Force plane bound for Kenya. The officials spoke on condition of anonymity because they weren't authorized to discuss the details of the operation.

The evacuation came after President Francois Bozize on Thursday urgently called on former colonial ruler France and other foreign powers to help his government fend off rebels who are quickly seizing territory and approaching the capital.

The U.N.'s most powerful body condemned the recent violence and expressed concern about the developments.

"The members of the Security Council reiterate their demand that the armed groups immediately cease hostilities, withdraw from captured cities and cease any further advance towards the city of Bangui," the statement said.

Central African Republic has a history of violent change in government. The current president himself came to power nearly a decade ago in the wake of a rebellion in this resource-rich yet deeply poor country.

Speaking to crowds in Bangui, a city of some 600,000, Bozize pleaded with foreign powers to do what they could. He pointed in particular to France, Central African Republic's former colonial ruler. About 200 French soldiers are already in the country, providing technical support and helping to train the local army, according to the French defense ministry.

"France has the means to stop (the rebels) but unfortunately they have done nothing for us until now," Bozize said.

French President Francois Hollande said Thursday that France wants to protect its interests in Central African Republic and not Bozize's government. The comments came a day after dozens of protesters, angry about a lack of help against rebel forces, threw rocks at the French Embassy in Bangui and stole a French flag.

Paris is encouraging peace talks between the government and the rebels, with the French Foreign Ministry noting in a statement that negotiations are due to "begin shortly in Libreville (Gabon)." But it was not immediately clear if any dates have been set for those talks.

French Foreign Minister Laurent Fabius spoke via phone with Bozize, asking the president to take responsibility for the safety of French nationals and diplomatic missions in Central African Republic.

Bozize's government earlier reached out to longtime ally Chad, which pledged to send 2,000 troops to bolster Central African Republic's own forces.

This landlocked nation of some 4.4 million people has suffered decades of army revolts, coups and rebellions since gaining independence in 1960 and remains one of the poorest countries in the world.

The rebels behind the most recent instability signed a 2007 peace accord allowing them to join the regular army, but insurgent leaders say the deal wasn't fully implemented. The rebel forces have seized at least 10 towns across the sparsely populated north of the country, and residents in the capital now fear the insurgents could attack at any time, despite assurances by rebel leaders that they are willing to engage in dialogue instead of attacking Bangui.

The rebels have claimed that their actions are justified in light of the "thirst for justice, for peace, for security and for economic development of the people of Central African Republic."

Despite Central African Republic's wealth of gold, diamonds, timber and uranium, the government remains perpetually cash-strapped. Filip Hilgert, a researcher with Belgium-based International Peace Information Service, said rebel groups are unhappy because they feel the government doesn't invest in their areas.

"The main thing they say is that the north of the country, and especially in their case the northeast, has always been neglected by the central government in all ways," he said.

The rebels also are demanding that the government make payments to ex-combatants, suggesting that their motives may also be for personal financial gain.