Interior Minister Goukouni Oueddei, strongman of Chad's provisional government, claimed today his forces have routed what he called "a Libyan invasion force" of more than 2,500 troops in a series of battles in the Tibesti Mountains of Chad's northern desert.

At least 11 rival dissident factions have been fighting intermittently in Chad for more then 12 years, and diplomatic observers believe that Goukouni's forces have probably engaged Chadian dissidents from one or more factions supported by Libyan cadres.

Goukouni said his forces took "numerous" Libyan prisoners, but admitted that a number of Chadian dissidents as well as some Egyptians and Sudanese were among the soldiers captured.

At a press conference earlier this week, Goukouni put three captured Libyan advisers on parade. The three are said to have admitted acting in an advisory capacity to Chadian dissidents opposed to the Goukouni government.

Goukouni told reporters today that the Libyans entered northern Chad in June with several motorized columns supported by French-made Mirage fighter-bombers.

The Chadian leader said the Libyans advanced as far as the area of Faya, a major military outpost in the desert, where several crucial battles took place in late June and early July.

Goukouni said his troops had little trouble defeating the Libyans in the Tibesti Mountains but that the Libyans still held a position north of the Tibesti range. He said this stronghold was supplied by C130 transport planes belonging to the Libyan Air Force.

An International Red Cross mission is in Faya to ensure that prisoners taken by Chad are well treated. Red Cross officials in Ndjamena declined to estimate the numbr of prisoners.

Goukouni chief of the Islamic Toubou tribe of northern Chad, became interim president of the country in April, after serving for less than a month as head of an eight-member State Council set up following the resignation of Chadian President Felix Malloum and Prime Minister Hissene Habre.

The council was formed under the terms of a peace agreement to end unrest in Chad, a landlocked Saharan nation of 4.2 million in north-central Africa. The agreement was signed in Kano, Nigeria, by leaders of several rival Chadian factions.

Goukouni, Chad's first non-Christian head of state since the end of French colonial rule in 1960, was previously leader of the Libyan-backed National Liberation Front (Frolinat) guerrillas. However, his nationalistic government has lost the support of the Libyans, who seek a Chadian government more receptive to Libya's territorial claims.

Libya and Chad have a territorial dispute dating back to a 1935 treaty signed by their former colonial rulers, Italy and France respectively.

The dispute involves 44,000 square miles of territory known as the Aouzou strip. The Strip was occupied militarily by Libyan troops in 1973 and later formally annexed to Libya, which has built schools and hospitals there. Residents of the area carry Libyan.

The disputed Azouzou strip is believed to hold uranium resources. CAPTION: Map, no caption, By Richard Furno - The Washington Post