Chadian aircraft on Saturday bombed the Nigerian town of Gamboru in a raid targeting Islamist extremist group Boko Haram, security sources said.
A raid was carried out around midday by two fighter jets on the town in Nigeria's far northeast along the Cameroon border, sources from Chad and Cameroon said on condition of anonymity.
Boko Haram overran the town several months ago as part of its campaign to seize territory in the region and create an Islamic state.
The Boko Haram uprising has become a regional crisis, with the four directly affected countries -- Cameroon, Chad, Niger and Nigeria -- agreeing to boost cooperation to contain the threat.
Nigeria's military said on Thursday that its fighter jets had bombed the northeast town of Malam Fatori, also controlled by Boko Haram.
Witnesses and some media reports said troops and airforce planes from Chad were also involved in that operation on Nigerian soil but Abuja neither confirmed nor denied the claim.
UN Secretary-General Ban Ki-moon on Saturday gave his backing to an African Union proposal to set up a regional five-nation force of 7,500 troops to fight Boko Haram.