Libyan planes bombed government forces in northern Chad again today while Libya continued supplying the rebel forces it backs in the recently recaptured town of Faya Largeau, informed sources here said.

The bombing attacks on the government-held town of Oum Chalouba and the large military buildup of the Libyan-backed forces in Faya Largeau, 220 miles northwest of Oum Chalouba, point to a renewed rebel effort to retake the strategic central town of Abeche.

Despite widespread reports to the contrary, Libyan leader Muammar Qaddafi consistently has denied direct Libyan involvement in Chad's civil war. Interviewed Friday night by ABC News, Qaddafi said "Libya has no military activities in Chad . . . . We don't want to overthrow the government of Chad; we want peace in Chad."

Since the the newest round of fighting in Chad's intermittent civil war began again in late June, the rebel forces of Goukouni Oueddei have captured Faya Largeau and Abeche--and been forced to retreat from both towns by President Hissene Habre's troops.

However, Goukouni's forces recaptured Faya Largeau Wednesday with help from a Libyan armored column that included tanks, said one informed source. The ground assault on the desert outpost, located 500 miles north of here, followed days of reportedly heavy bombing by Libyan combat aircraft. Government officials have said that "several hundred" civilians were killed in the bombings.

Libyan officials said in Tripoli that rebel forces had captured Oum Chalouba and two other towns, Biltene, northeast of Ndjamena, and Koro Toro, 350 miles to the north on the main road leading to the capital, United Press International reported. There was no confirmation of the claim.

By reportedly introducing its tanks and armored cars into the conflict, Libya appears to be increasing the stakes in its drive to put ex-president Goukouni into power.

Qaddafi's apparently renewed military activity follows increased U.S. and French arms supplies to Habre's comparatively weaker forces. The French commitment includes up to 300 paratroop "advisers" and tons of military equipment and rockets. President Reagan has authorized the delivery of $25 million in military aid to the embattled Habre government, plus 30 Redeye antiaircraft missiles. At least some of the missiles have been delivered to Chad, but reportedly have not been used in combat.

Foreign observers here view the reported Libyan bombing of Habre's troops at Oum Chalouba and the influx of new military supplies into Faya Largeau as military moves presaging a new drive to capture Abeche. Oum Chalouba is on the road to Abeche.

Foreign observers here say the fall of Abeche could allow Libyan armored columns to move from Faya Largeau and Abeche toward Ndjamena, Chad's capital.

Although France has dispatched a unit of paratroopers to Chad and continues to send military supplies to the government forces, it is unclear whether President Francois Mitterrand will go any further to save the embattled Habre government.

A 1976 defense treaty between the two countries calls only for arms and logistical support. However, during the past few days Habre has renewed his call for France to directly intervene with combat aircraft and troops, if necessary.

President Reagan has already said he will not directly intervene in Chad and considers the former French colony to be within the French sphere of influence and responsibility.

However, for strategic reasons the United States would like to stop Qaddafi from gaining a foothold in Chad. U.S. officials fear that a Libyan presence in Chad would aid Qaddafi's continuing efforts to destabilize U.S. allies Egypt and Sudan.

The United States relies heavily on Egypt and Sudan as bases for its Rapid Deployment Force. This month, in fact, American armed forces are holding joint military maneuvers with Egypt, Sudan and Somalia.

France has been at odds with Qaddafi for a decade over the latter's efforts to destabilize the governments of several former French colonies in the region, including Niger and the Central African Republic. Cameroon and Nigeria also are worried about Qaddafi's intentions in the region. All four countries share borders with Chad.

Qaddafi wants to create a revolutionary, pan-Islamic empire in northern Africa led by Libya. Qaddafi's Soviet-supplied arsenal includes about 3,000 tanks including modern T72s, 550 combat jets and 30 armed helicopters--all bought with Libya's oil income.