NDJAMENA, Chad — A rebellion aimed at toppling Chad’s president appeared to falter Tuesday as France declared that it would intervene to protect the Chadian government if called upon, and a Darfur rebel group with close ties to the Chadian government said it had sent troops to help bolster the president, Idriss Déby.

French military officials in Chad said the rebels were far from Ndjamena, the capital, and the streets of the city were quiet. For the first time since the weekend, the sound of automatic gunfire disappeared. But the streets were virtually empty — many thousands have fled into neighboring Cameroon, and most people who remained stayed indoors, according to French soldiers who patrolled the city.

The bodies that had been putrefying in the streets were removed, but evidence of the previous day’s gun battles remained in the blackened husks of pickup trucks used by government and rebel fighters.

Recent fighting in the city has left at least 1,000 people wounded, a spokesman for the International Red Cross said Tuesday, citing reports from a team that visited several hospitals in Ndjamena, but it could give no estimate of the numbers killed by the fighting and cautioned that many of the wounded might not have been able to reach hospitals.

French support, along with help from fighters of a Sudanese rebel group with ties to Mr. Déby’s family, strengthened the government’s position markedly.

Responding to questions from journalists in France as to whether French soldiers would intervene to help Mr. Déby’s government, the French president, Nicolas Sarkozy, said: “If France must do its duty, it will do so. Let no one doubt it.”

A commander from the Justice and Equality Movement, a Darfur rebel group that has been fighting Sudan’s government and its allied militias in the war-ravaged region for the past five years, said some of the rebel troops had left their base in eastern Chad, along the border with Sudan, to reinforce Chadian government troops.

The addition of Darfur rebels to the fray adds new confusion to a tangle of conflict in Chad and Sudan, two of the most violent African countries. They have accused each other of fostering rebellions against them, and events in recent days point to evidence that both are probably right.

The Chadian rebels once advancing on Ndjamena have found shelter in Sudan, something that would certainly require Sudanese government approval, analysts and diplomats say. The Darfur rebels operate openly in eastern Chad, though this is the first time they have publicly admitted to helping Mr. Déby militarily.

Despite what was apparently the retreat of the rebels, the situation remained tense. Government television and radio remained off the air, and cellphone networks that were taken down to hamper rebel communication were still off Tuesday.

At least four leading opposition figures have been arrested in the past few days, including Ngarlejy Yorongar, a member of Parliament who once lost a presidential election to Mr. Déby. Reed Brody, a lawyer at Human Rights Watch, said government soldiers had burst into Mr. Yorongar’s house, shot and wounded his driver and hauled off Mr. Yorongar, one the government’s most strident critics. Three other opposition leaders were also arrested, and none have been heard from since Sunday, human rights workers said.

“These opposition leaders are at grave risk of being tortured or forcibly disappeared,” Tawanda Hondora, director of the Africa program for Amnesty International, said in a statement. “The Chadian government seems to be using the current conflict with the armed opposition as a cover for arresting people peacefully opposed to government policy.”

Up to 20,000 people have fled across the Chari River to the town of Kousseri, in Cameroon, according to staff members of the United Nations refugee agency, who reached it on Monday.

The agency was preparing for the arrival of more refugees. Some had found shelter with relatives, others at schools, but 6,000 to 7,000 had reached a former refugee camp near the river and were the most vulnerable, most of them spending the night in the open, the agency said.

Despite the lull in the fighting on Tuesday, agency staff members said civilians were still moving toward Cameroon, while others searched for food and other supplies that have become increasingly scarce and expensive.

The agency said it was about to airlift 90 tons of supplies to Cameroon from Dubai and was preparing to move people to a site that can hold up to 100,000 people.