More than 130 Boko Haram Islamist fighters have surrendered to Nigerian forces, and a man posing as the group’s leader in numerous videos had been killed in clashes, the military said on Wednesday. The army has stepped up military operations against Boko Haram in the remote northeast since the rebels seized several small towns and declared the area they control a “Muslim territory”. The military said that 135 Boko Haram members surrendered with their weapons in Biu, Borno State, on Tuesday - and that 133 others surrendered elsewhere in north-eastern Nigeria and were being interrogated. Boko Haram has suffered heavy losses in recent weeks as the Nigerian military battled the group close to its hometown of Maiduguri in the north east. The group, which has killed thousands in five years of hit-and-run attacks on military installations and civilians has grown increasingly ambitious in the past two months and started trying to take and hold ground in Africa’s largest oil producer.