A fighter jet

Chadian aircraft struck Boko Haram positions in the Nigerian border town of Gamboru for a second straight day on Sunday, an AFP journalist in a neighbouring town said.

Two military choppers pounded targets in Gamboru for about two hours, setting off loud explosions and sending thick clouds of smoke into the sky, the journalist said from the town of Fotokol about 500 metres (yards) away.

The town in far northeastern Nigeria, on the border with Cameroon, was already strafed by two Chadian fighter jets on Saturday, in a raid targeting extremist group Boko Haram, security sources said, as regional efforts to combat the Islamists intensified.

An initial raid was carried out around midday on Saturday 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.

It was followed by further bombings of areas around the town, Chadian sources said. The raids were aimed at “allowing Chadian soldiers to enter Gamboru,” a Cameroon security source told AFP.

Details on damage or casualties were not immediately clear.

Boko Haram overran the town several months ago as part of its campaign to seize territory in the region and create an Islamic state.

“Senior officers from the Cameroon army are located in Fotokol,” the Cameroon source said. “The Cameroon and Chadian armies met for the Gamboru operation.”

The Cameroon town of Fotokol and its surroundings, just across the border from Gamboru, saw fighting between Chadian soldiers and Boko Haram extremists on Thursday and Friday.

Chad’s military said three of its soldiers and 123 militants were killed in the two days of fighting in the area.

Chad has deployed soldiers to Cameroon to help in the fight against the Islamists.

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.