The government of Chad tonight accused Libya of bombing the desert outpost of Oum Chalouba in "revenge" for a setback suffered by rebel forces last week when they tried to overrun the government garrison at the oasis.

It was the first reported action by Libyan warplanes since France sent a task force of more than 2,000 troops to its former African colony in mid-August. Before the French intervention, Libyan jet planes had been involved in almost daily raids against Oum Chalouba and other towns in northern Chad.

Oum Chalouba, which in normal times is little more than an uninhabited crossroads, lies outside the defensive perimeter or "red line" set up by the French along the 15th Parallel. French military sources in the Chadian capital, Ndjamena, said that none of the 12 French Mirage F1 and Jaguar fighter-bombers in Chad intervened in today's fighting.

The French planes were reported to have played a decisive role Friday in intimidating hundreds of Libyan-backed rebels who attacked the government garrison in Oum Chalouba, which is 400 miles northeast of the capital. The rebels were reported by western military sources in Chad to have scattered into the desert when three French Jaguars roared overhead without firing any shots.

In an interview with western journalists Saturday in Bardai in northern Chad, rebel leader Goukouni Oueddei insisted that his forces were in control of Oum Chalouba and accused the French of launching bombing raids. He was quoted as saying that "war has started between us and the French" and that he might have to "call for help."

The Chadian government rejected an oblique offer by Goukouni to negotiate if French troops stationed here were withdrawn and reiterated that it would negotiate only with Libya, Reuter reported. Information Minister Soumaila Mahamat said Goukouni made the offer during his meeting with journalists in Bardai.

The Libyan planes involved in today's reported attack on Oum Chalouba presumably came from Bardai, since there is no Libyan-controlled airstrip closer to Oum Chalouba suitable for jet planes. Bardai is about 600 miles from Oum Chalouba--a fact that severely limits the amount of time Libyan planes can remain over the target.

Soumaila said that the attack had involved Soviet-made MiG and Sukhoi fighter-bombers and had lasted for 30 minutes. He added that it had caused casualties among the "civilian population" of the oasis.

It was impossible to verify these claims as no western reporters are allowed to travel to the battle zone. In the past, the Chadian government has frequently exaggerated the extent of the fighting as a means of attracting greater support from the West.

Officials in Paris have played down the latest fighting, saying they regarded it as part of a "war of nerves" rather than a prelude to a general Libyan-led offensive. The French have made it clear that they regard Oum Chalouba as practically indefensible, but would respond vigorously if their own positions came under attack.

The Paris office of the rebels' "Transitional Government for National Unity" issued a statement today reiterating claims that its forces were still in control of Oum Chalouba and denying that there had been a Libyan air attack. "Such an attack would be tantamount to bombing our own positions," the statement said.