At least four people were killed in northeast Nigeria on Thursday in a suicide blast at an open-air mosque, militia and refugee camp officials told AFP. The suspected Boko Haram bomber, who requested anonymity, was disguised as a worshipper, detonated his explosives at a camp for people displaced by the insurgency in Dikwa, a town 90km east of Maiduguri, the Borno state capital. "Early this morning a suicide bomber killed four people and injured 15 others when he detonated his explosives as people gathered to pray at the '1 000' camp in Dikwa," militia leader Babakura Kolo told AFP.An official at the camp, who , said that "the attack by a male suicide bomber happened at 05:17 (0415 GMT)"."We lost four people in the attack and 15 others sustained injuries and are in hospital receiving medical care," he said.Dikwa is home to more than 70 000 displaced people from the war-torn region who live in several camps scattered across the town, relying on food handouts from aid agencies to survive.The attack came two days after a suicide bomber killed five militia members fighting Boko Haram jihadists in the town of Konduga, which lies 35km southeast of Maiduguri. Boko Haram's nine-year quest to carve out an Islamic state in northeast Nigeria has led to the deaths of 20 000 people and forced hundreds of thousands more from their homes.The militant group has been weakened since it controlled swathes of territory in 2014 but attacks still persist.The jihadists frequently use suicide bombers, many of them women and young girls, to target military checkpoints, mosques, markets and other crowded places.On May 1, an estimated 86 people were killed in twin suicide blasts targeting a mosque and a nearby market in the town of Mubi in neighbouring Adamawa state.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.