Niger, Chad attack Boko Haram after IS pledge of allegiance

Niger and Chad on Sunday launched major ground and air strikes in northeast Nigeria against Boko Haram, after the militants formally pledged allegiance to the Islamic state group in Syria and Iraq.

The attacks, which follow a sustained build-up of troops in southern Niger, opens up a new front in regional efforts to wipe out the Islamist group, whose six-year insurgency has spread across borders.

"Very early this morning, troops from Niger and Chad began an offensive against Boko Haram... in the area of Bosso and near to Diffa," a Niger government source in Niamey told AFP on condition of anonymity.

More than 200 vehicles, some of them with machine guns, as well as tanks, ambulances, water tankers and transport trucks, were seen moving towards the border, radio station Anfani, based in Diffa, said.

Aircraft targeted Boko Haram positions on Saturday and early Sunday, it added, while a Diffa resident and aid worker said troops were seen heading to the border and heavy gunfire was heard.

The previously lacklustre counter-insurgency against Boko Haram has been given renewed vigour with the deployment of troops from Cameroon, Chad and Niger last month.

The armies have claimed a series of successes in rebel-held territory in recent weeks, as part of an operation to clear and control northeast Nigeria in time for general elections set for March 28.

Much of the focus has been on Chad's well-trained army, who have experience in tackling Al-Qaeda-linked extremists in Mali alongside French forces.

But Nigeria's military spokesman Chris Olukolade said the Nigerien and Chadian attacks were "complementary to the ongoing push against the terrorists" that it was heading.

"The mission of routing the terrorists from Nigeria's territory is being conducted from various fronts in and out of Nigeria and is achieving expected results so far," he said in a text message.