The U.N. Security Council urged countries on Monday to support Chad's government against rebels, opening the way for foreign aid to help thousands who have fled a two-day assault on the capital.

The riverside city was deserted as dusk fell. The remaining residents were fearful that some 2,000 rebel fighters, who want to topple President Idriss Deby to end what they call a corrupt and dictatorial rule, might return. They withdrew on Sunday.

Pickups crammed with soldiers patrolled the streets and army helicopters flew overhead after two days of clashes which left hundreds wounded. Bodies and abandoned vehicles littered the capital of the oil-producing, central African state.

In New York, a non-binding U.N. Security Council resolution urged the international community to support Deby, giving a green-light to France to answer Chad's appeals for foreign aid.

"The Security Council calls upon member states to provide support in conformity with the United Nations charter as requested by the government of Chad," the council said.

France, the former colonial power which has troops stationed in Chad, previously said it would remain neutral. But President Nicolas Sarkozy appeared to harden his stance on Monday, saying France could intervene more directly if it had U.N. approval.

"The situation in Chad is alarming because Chad has a legitimate government elected at the ballot box," Sarkozy told a news conference during a visit to Romania.

The rebel attack, which Chad said was backed by neighbouring Sudan, forced the European Union to delay the deployment of a peacekeeping force to eastern Chad to protect more than 200,000 refugees from the war in Sudan's Darfur region. EU foreign policy chief Javier Solana said this was a temporary measure.

Deby's government, reeling from the second strike on the capital in two years, claimed a military victory on Monday. But the rebels, who denounce his 18-year rule as corrupt, said their withdrawal late on Sunday was tactical.

Timane Erdimi, leader of one of the groups in the rebel coalition, said they had pulled back to face pro-Deby fighters from Sudan's Darfur region, who were racing to the president's aid across some 800 km (500 miles) of scrub from the east.

Aid workers in eastern Chad said a large column of fighters from the Darfur's rebel Justice and Equality Movement (JEM) had passed the eastern town of Abeche and was rushing to N'Djamena.

"BATTLE IS OVER"

Before withdrawing late on Sunday, rebel fighters had gone from house to house in some areas, telling occupants to leave because they planned to attack again. Thousands of refugees poured across the Ngueli bridge over the Logone-Chari river into Cameroon after dawn, carrying belongings and children.

Some were hurt, including a girl with a bullet wound in the back. Local Cameroon authorities estimated some 15,000 people had fled across the river to the small border town of Kousseri.

A Reuters TV correspondent who crossed into N'Djamena from Cameroon via the bridge saw 12 bodies, some in uniform, lying in the streets. There was evidence of widespread looting of cars and homes.

"The battle of N'Djamena is over," Foreign Minister Ahmat Allam-mi told French radio.

Chad says the rebels, who include some of Deby's former allies and family members, are armed by Sudan. Khartoum denies this and accuses Chad of supporting the five-year uprising in its Darfur, where more than 200,000 people have died.

Chad's army said it repulsed an assault by Sudanese army troops and rebels on the frontier town of Adre on Sunday. Sarkozy ordered French fighter jets to survey the border area with Sudan to ensure there is no "foreign incursion".

With the political opposition and rebel groups divided by ethnic and personal rivalries, foreign diplomats have expressed fears that Chad could plunge into prolonged instability if Deby, who has won three widely-criticised elections, were toppled.

As the fighting subsided in N'Djamena, soldiers rounded up leading opposition members, including opposition coalition spokesman Ibni Oumar Mahamat Saleh, family members said.

Aid organisations such as Oxfam pulled some foreign staff from the country following the escalation in fighting, placing further strain on overstretched humanitarian operations.