Burkina Faso said last night that its Air Force had launched a raid on the southern Malian town of Sikasso in a further escalation of the war between the two neighboring West African states.

Ougadougou radio, monitored here, described the air attack on the town, which is about 30 miles inside Malian territory, as a just response to Christmas Day air attacks by Mali on Burkina Faso civilian targets, Reuter reported.

Earlier, Burkina Faso, known until last year as Upper Volta, reported heavy fighting on its border with Mali and said it had inflicted a crushing defeat on Malian troops.

A cease-fire was announced early today by Libyan Foreign Secretary Abdul Salaam Treiki in Ouagadougou, according to a Burkina Faso radio broadcast monitored by the British Broadcasting Corp. in London.

[Treiki, who has been shuttling between Ouagadougou and the Malian capital of Bamako in search of a settlement to the escalating desert conflict, said the cease-fire would start at midnight local time last night.]

In Bamako, a military communique made no mention of renewed fighting but said one Malian soldier and 20 from Burkina Faso had died in the conflict.

The countries went to war Christmas Day over a mineral-rich area 120 miles north of Ouagadougou.