N'DJAMENA, Chad (AP) _ President Hissene Habre fled the country Saturday following a string of rebel victories, and the Libyan-armed guerrilla fighters later marched into the capital, Western diplomats said.

Habre and much of his government sought refuge in neighboring Cameroon, the diplomats said.

As the rebels closed in, soldiers threw away their guns and uniforms, leaving the city practically undefended. There was wild looting in the capital, N'Djamena, by civilians and renegades from the Chadian army.

France began organizing the evacuation of French and other foreign nationals living in this north-central African nation, a former French colony.

It was not immediately known how many rebels marched into the city, but it appeared they were mainly advance patrols. Most guerrillas seemed to have remained in eastern Chad, where they have made significant incursions.

The rebels' biggest victory has been the capture Thursday of Abeche, an eastern town of about 30,000 people 500 miles from N'Djamena.

The rebels, led by former armed forces chief Idriss Deby, are armed by Libya, but there was no indication the North African nation was involved in the latest fighting.

Libya, which has made historical claims to parts of Chad, denies involvement in the rebel offensive, which began Nov. 10.

Deby helped Habre, 48, oust former President Goukouni Oueddei from power in 1982.

The French news agency Agence France-Presse cited sources in N'Djamena as saying Deby would march into the capital Sunday at the head of an army of guerrillas and government deserters.

Alingue Bawayeu, president of Chad's National Assembly and apparently the highest-ranking government official left in N'Djamena, appealed for calm in an address on Radio Chad. He said negotiations were under way with Deby.

Bawayeu, who is under the protection of French troops, said he was leading an interim government comprised of National Assembly members and urged soldiers to lay down their weapons.

Western diplomats in N'Djamena and high-ranking sources in Paris, all speaking on condition of anonymity, said Habre and his family fled to neighboring Cameroon in a military transport plane before dawn Saturday.

They said government ministers and their entourages escaped across a bridge into Cameroon, just west across the Chari River from N'Djamena.

Some officials remaining in the capital said Habre had left N'Djamena to direct attacks against rebel forces.

Troops deserted en masse after rumors spread of Habre's flight. Angry citizens attacked government buildings or fled to Cameroon.

Military boots and uniforms littered the roadsides, apparently left behind by deserters hoping to avoid reprisals from the rebels.

Many soldiers turned their rifles on motorists and commandeered cars for the trip to Cameroon or Nigeria, which lies further west across the northern tip of Cameroon.

Others threw away their weapons, which were quickly picked up by looters, who fired them into the air and went on rampages. Renegade troops and civilians ransacked shops and houses setting fire to them or stealing belongings.

Political detainees and common criminals broke out of the city's central jail, with little opposition from jailers.

Less than three years ago, the capital city of 400,000 was re-built after suffering heavy damage from fighting in 1978, 1979 and 1982.

About 1,000 foreigners, mostly French, assembled at the N'Djamena airport to be evacuated. A Boeing 747 was to arrive with the first 500 or so in Paris on Sunday morning, with another to follow shortly.

In Washington, State Department spokeswoman Anita Stockman said an unspecified number of Americans will be leaving N'Djamena on the French- chartered planes and commercial flights bound for Paris on Sunday and Monday.

However, a U.S. Embassy spokesman said that no orders to leave had been given for the 300 Americans living in Chad. French officials did not expect many to be aboard.

''We are suggesting it is probably a good idea to leave now, but it would only be voluntary,'' said the U.S. Embassy spokesman. ''There are lootings and firings, but I'm not aware of anybody being hurt.''

The Libyan news agency JANA, monitored in Rome, carried a communique by Deby's Popular Salvation Front that promised no reprisals against his opponents and urged foreigners not to leave.

''We reassure foreign nationals not to worry for their lives and property,'' the JANA dispatch cited the communique as saying.

France said Saturday it was sending 150 more Foreign Legionnaires to bolster Operation Sparrowhawk, a permanent French force first sent in 1986 when Libya threatened to capture N'Djamena. At one point, French troops in Chad numbered 2,700.

About 1,000 French troops are now stationed here under a defense agreement.

Paris has said that the current fighting is among Chadians, and it will not interfere.

Chad contends the rebels, based in neighboring Sudan, are backed by Libya, which occupied two-thirds of Chad in 1980 after Habre was defeated by Goukouni in another power struggle.

The Libyans withdrew in November 1981 but made incursions from the north in August 1983. In 1986, Libya moved further into northern Chad, occupying much of the region known as the BET - the initials of its three departments.

Despite a peace treaty signed in 1989, Chad and Libya continue to dispute a Libyan-occupied strip of land on the northern frontier of this nation of 5.2 milion people.

Deby, a highly regarded military strategist, was the mastermind of a series of lightning attacks the following year that drove the Libyans from the area.

He and several other high-ranking officials were charged by Habre with attempting a coup in April 1989. Deby escaped and established a base in eastern Sudan.