NDJAMENA, CHAD, DEC. 1 -- Guerrilla fighters marched into this capital after President Hissene Habre fled the country today, Western diplomats said.

Habre and much of his government sought refuge in neighboring Cameroon, the diplomats said. The French government began organizing the evacuation of their citizens and other foreign nationals living in this north-central African nation, a former French colony.

The Habre government had insisted that the three-week rebellion led by former armed forces chief Idriss Deby was being funded, armed and directed by Libya. Earlier this week the United States called the uprising "the latest example of Libya's ongoing efforts to destabilize legitimate governments." Libya has denied any involvement.

The French government, which has about 1,000 foreign legionnaires stationed in Chad and sent 150 paratroops to bolster the force, called the rebellion a personal vendetta between Deby and Habre. Deby helped Habre oust former president Goukouni Oueddei in 1982 but was charged with attempting a coup against Habre in April 1989. Deby escaped and established a base in eastern Sudan, from where he launched his offensive Nov. 10.

It was not immediately known how many rebels marched into the city today, but they appeared to be advance patrols. The Agence France-Presse news agency, citing sources in Ndjamena, said Deby would march into the capital Sunday at the head of a force of guerrillas and government army deserters.

Western diplomats in Ndjamena 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 today. They said government ministers and their entourages escaped across a bridge into Cameroon, just west across the Chari River from Ndjamena.

Alingue Bawayeu, president of Chad's National Assembly and apparently the highest-ranking government official left in Ndjamena, appealed for calm in an address on Radio Chad. Bawayeu, under the protection of French troops, said he was leading an interim government composed of National Assembly members and had opened negotiations with Deby.

Troops deserted en masse after news spread of Habre's flight, and looting was reported in the capital.

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.

But the French Embassy started assembling 1,000 French nationals in the capital, and it appeared that France also would organize the evacuation of other foreigners. About 300 Americans are in Chad.