Chad's army said its forces had killed hundreds of Boko Haram fighters and lost nine of its own troops in clashes in northern Nigeria.

Soldiers from Chad and Niger drove the group from Malam Fatori, one of Boko Haram's last major footholds near Nigeria's border with Niger, earlier this week. Wednesday's clashes took place as they were mopping up the area in Nigeria's Borno state.

Niger military sources just across the border said air strikes began before an offensive by ground troops.

"There was fighting and we recorded nine dead and 16 injured. There were hundreds of dead on Boko Haram's side," said Colonel Azem Bermandoa, a spokesman for Chad's army, on Wednesday.

Bermandoa said the fighting had driven the group's fighters more than 10km outside the town, which had been held by Boko Haram since November. There was no immediate comment from Niger's army on any casualties.

Boko Haram wants to create a caliphate in the north-east Nigeria, and thousands of people have been killed since 2009 when the group launched an armed rebellion against the state.

An offensive by Nigerian, Chadian and Nigerien troops this year has since pushed the group out of most of the towns they previously controlled.

The armed group failed to deliver on threats to cause havoc during the just-concluded presidential election that was won by former army general Muhammadu Buhari.

The president-elect Buhari promised on Wednesday to "spare no effort" to defeat the group, which seized swathes of territory under outgoing president Goodluck Jonathan.

Source: Reuters