NIAMEY (Reuters) - Troops from Chad and Niger have discovered what appears to be a mass grave outside the northern Nigerian town of Damasak, liberated from the Islamist group Boko Haram at the weekend, Niger military sources said on Friday.
The sources said investigations were underway to establish the number of bodies and that they were awaiting the arrival of Nigerian authorities to take charge of the operation.
"Niger and Chad's troops have discovered a mass grave at Damasak, which appears to contain the bodies of Boko Haram's victims," said one of the military sources, who asked not to be identified.
The dusty streets of Damasak were largely deserted following its liberation on Saturday, after many inhabitants had fled the Islamists' four-month rule. Shops and businesses were looted and Boko Haram's black and white insignia were scrawled on buildings around the town.
The military sources said they had requested Nigeria's military to occupy the town, which lies close to the border with Niger, but had yet to receive a response.
"As far as I know, as of yesterday, the Nigerian army has still not arrived in the area. We are waiting," said one of the sources.
The regional offensive launched this year by Chad, Niger, Cameroon and Nigeria comes as Africa's most populous country and biggest economy prepares to hold presidential elections on March 28.
At the start of this year, Boko Haram controlled around 20 local government areas, a territory the size of Belgium. With the help of foreign allies, Nigeria's army said on Tuesday it pushed the rebels out of all but three districts.
President Goodluck Jonathan has been criticized for not doing enough to tackle the insurgency. His challenger Muhammadu Buhari has campaigned on a reputation for toughness gained when he was military ruler of Nigeria in the 1980s.
(Reporting by Abdoulaye Massalaki; Writing by Daniel Flynn; Editing by Crispian Balmer)