Chadian troops clashed with Boko Haram fighters in the northeastern Nigerian town of Gambaru on Tuesday in a bid to liberate it from the Islamists, according to military sources from Chad. "Our troops entered Nigeria this morning. The combat is ongoing", one of the sources said. Chad is said to have deployed about 2,500 soldiers to its neighbor.

The Nigerian military, that was widely criticized for failing to stifle Boko Haram's insurgency, claimed that the town of Gambaru had already been liberated on Monday.

The Islamist group Boko Haram launched its military operations in 2009, with the goal of creating a caliphate in Nigeria which would also incorporate parts of Chad, Cameroon and Niger. Since 2009, the Islamists killed more than 13,000 people and abducted hundreds, including at least 200 schoolgirls from the Nigerian town of Chibok.

The African Union (AU) authorized a force of 7,500 troops from Nigeria, Chad, Cameroon, Niger and Benin to fight Boko Haram. Chad's 2,500 soldiers will form part of that force.

According to Reuters, French military aircraft are carrying out surveillance missions to help countries bordering on Nigeria deal with Boko Haram.

das/rc (Reuters, AFP)