Libyan leader Muammar Qaddafi reportedly ordered the "immediate" withdrawal of all Libyan troops from war-torn Chad yesterday in a move coinciding with a Franco-African summit that is seeking to coordinate support for the embattled central African country.

The Libyan decision came five days after Chadian President Goukouni Oueddei asked Qaddafi to withdraw his troops from Chad by Dec. 31, and one day after Chadian rebels opposing the Libyan-backed regime announced they were suspending their guerrilla warfare.

Agence France-Presse reported yesterday from the Chadian capital of Ndjamena that the Libyan Army's commander-in-chief, Col. Radwan Salah Radwan, said Qaddafi had told him in a telephone conversation to leave the country "immediately." The withdrawal, if it occurs, would take three to four days, informed sources reported.

State Department sources said there are approximately 7,000 Libyan troops in Chad, while one French source said the number is considerably higher.

The Libyan troop presence in Chad has been a major source of tension in the northeast corner of Africa for almost a year, and has been perceived as a threat by both neighboring Sudan and Egypt. Since the assassination of Egyptian president Anwar Sadat, the United States has frequently cited the Libyan troops as a justification for increasing U.S. military aid to the Egyptian and Sudanese governments.

There were reports yesterday of Libyan troop withdrawals by airplane from Ndjamena Airport both from the French news agency and, according to State Department officials, from an American CBS film crew located in the northern Cameroon village of Kousseri, across the Chari River from Ndjamena.

At the Franco-African summit in Paris, Chadian President Goukouni said that "the Libyan troops were leaving at the request of Chad," according to a United Press International report.

"The Libyan withdrawal answers our wish for an immediate pullout from Ndjamena," Goukouni continued. "They Libyan troops have transport means at their disposal" for a speedy withdrawal, Goukouni added.

The Chadian fighting and Libya's involvement in it have been high on the agenda of the eighth Franco-African summit in Paris this week, which is being attended by 19 African heads of state and high-level delegations from another 12 African countries.

French President Francois Mitterrand has been urging the Organization of African Unity to speed up the organization of the continent-wide group's proposed peace-keeping force for Chad. Mitterrand has promised that France, the former colonial power in Chad, will pay part of the cost for the force, a major stumbling block to getting the two-year-old proposal off the ground.

OAU Chairman Daniel arap Moi, the president of Kenya, recently told Mitterrand that formation of the force is nearing completion. Two of Chad's immediate neighbors, Nigeria and Cameroon, as well as Egypt, Senegal and the Ivory Coast have offered to contribute to the force. The multinational nature of the peace-keeping force reflects the concern African leaders have expressed about Qaddafi's intentions in Chad and the surrounding region.

Libyan troops entered Chad last November at Goukouni's invitation to end a nine-month-old, bloody civil war between government forces, made up of a 10-faction coalition, and an 11th faction headed by former defense minister Hissene Habre. The intervention of the Libyans was decisive and Habre's guerrilla forces were driven from the Ndjamena capital on Dec. 15.

Then, Qaddafi and Goukouni announced in early January that the two countries would be merged. Informed sources at the time felt that Goukouni had been pressured into the merger agreement because his shaky coalition government was totally dependent on Qaddafi's troops. The merger announcement was hastily rescinded by Qaddafi after African leaders accused the mercurial Libyan leader of trying to annex Chad as part of his dream to unite all of northern and central Africa into a Qaddafi-led, pan-Islamic nation.

Over the past year, Qaddafi's soldiers and Goukouni's troops have repeatedly clashed around the eastern Chadian city of Abeche. Chadian Foreign Minister Ahmat Acyl, a strong supporter of Qaddafi's, has at times had his faction's soldiers side with the Libyans against Goukouni's.

To complicate matters, all of the forces have been engaged in battles against the defeated guerrillas supporting Habre, who, driven out of eastern Chad over the past year, have established bases in western Sudan. It was Habre who announced in Sudan Monday that his forces were suspending their activities as the Franco-African summit opened.

Sudanese President Jaafar Nimeri has accused the Libyans of bombing both sides of the Chadian-Sudanese border. After Sadat's assassination, Nimeri publicly accused Qaddafi of preparing to invade Sudan from Chad.

Tensions also rose simultaneously along the Libyan-Egyptian border and President Reagan ordered two AWACS (Airborne Warning and Control System) aircraft to Egypt to patrol the boundary between the two antagonists. Both Egypt and Sudan, with alleged American backing, have been supporting Habre's guerrillas against Goukouni's government out of fears of Libyan intentions in Chad. It was unknown early yesterday how the two governments reacted to the reported Libyan troop withdrawal.

France, the former colonial power in Chad, was reported to have secretly backed Habre under former president Valery Giscard d'Estaing, but shortly after his election last May, Mitterrand indicated that his government would respect and follow the OAU recognition of Goukouni's coalition government.