Government troops using tanks and attack helicopters repelled a rebel assault on Chad's capital Thursday. The president assured residents he remained in control, and he blamed Sudan, whose Darfur crisis has spilled over into his country.

The pre-dawn attack on N'Djamena demonstrated how little control President Idriss Deby has outside his capital in a tumultuous part of the world where rebel groups cruise the desert at will.

Rebels from the United Front for Change drove 620 miles in pickups from their bases on the eastern border with Sudan's Darfur region and launched the attack just weeks before presidential elections in Chad, Africa's newest oil-producing country. Sudan denied backing the rebels.

Troops were waiting on the outskirts of the capital, and within hours, Deby declared that the rebels had been defeated, though few in the country were assured the fight for control of Chad was over.

An Associated Press reporter saw 10 bodies in the streets, and residents reported seeing many more.

Gen. Mahamet Ali Abdullah, speaking on state-run radio, claimed that government forces had killed hundreds of rebels, and he said troops were holding 20 rebel prisoners. Four tanks guarded the presidential palace.

Chad, a majority Muslim nation of 10 million in north central Africa, shares a border with Libya and Sudan. It recently began exporting oil, and rebels want control of the lucrative reserves — Chad's only real resource.

An Exxon Mobil-led consortium exported 133 million barrels of oil from Chad between October 2003 and December 2005, according to the World Bank, earning Chad $307 million.

Deby has seen his authority undermined since the discovery of oil and the violence began in Sudan, where the government is accused of unleashing Arab tribal militias against African rebels and civilians.

Scores of defectors from Chad's army have joined rebel groups in a bid to overthrow Deby, who himself seized power in a 1990 coup. Dissident troops also tried to overthrow Deby in March. Loyalist forces arrested more than 100 people for their alleged involvement in the attempted coup, launched while the president was out of the country.

The arid, landlocked nation about three times the size of France has been wracked by violence for most of its history, with more than 30 years of civil war since independence from France in 1960 and different small-scale insurgencies since 1998.

Interference by neighbors has added to Chad's volatility. Libyan leader Moammar Gadhafi has backed several Chadian rebel groups. Libyan troops entered Chad in 1981 and remained in the country until 1986.

More than 200,000 refugees from Darfur have sought protection in eastern Chad, and Sudan's government has accused Chad of supporting Darfur rebels fighting with government-backed militia.

Rights groups have said Chadian and Sudanese militias in Darfur have launched frequent cross-border raids, killing Chadian civilians. Deby has been accused by Chadians of doing too little to help Sudanese in Darfur who share ethnic links with many Chadians.

The United Nations expressed alarm over the possible impact of the violence on refugees.

"I urgently appeal to all sides in this political upheaval to respect the civilian character of the refugee camps and to leave in peace those who have already fled the terrors of Darfur," said Antonio Guterres, U.N. High Commissioner for Refugees.

Deby said on state-radio that the men who attacked the capital were mercenaries paid by Sudan to overthrow him before he can hold elections May 3. The path to power in Chad via Darfur is something Deby knows well. He launched his 1990 rebellion from Darfur.

Thursday's fighting began before dawn, with residents in eastern neighborhoods waking to heavy gunfire. Government helicopters fired rockets at rebel positions, and tank fire and mortar rounds echoed through the city.

France sent 150 troops Wednesday to bolster its contingent of about 1,200 already in Chad to protect about 1,500 French citizens there, the French Defense Ministry said.

President Jacques Chirac spoke with Deby, a Chirac aide said, and advised him to alert the U.N. Security Council, which he did. The Chad fighting was expected to come up in Thursday's consultations at the United Nations, the aide said on condition of anonymity because he wasn't authorized to speak about the issue publicly.

French fighter jets carried out reconnaissance missions over Chad Wednesday and Thursday to assess any threats and better protect French citizens, the ministry said. Col. Gerard Dubois, a spokesman for the French military, strongly denied French radio reports that French military fighters carried out bombardments in eastern Chad.

Chad and its former colonial ruler remain close, and France is a strong supporter of Deby. France has a cooperation agreement with Chad but a special decision would be needed for French forces to enter combat.