At least 15 people were killed in an attack by gunmen in Nigeria's southwestern state of Ogun, sources said.Baale Musa Ogundare, a traditional chief in Imushin community at Ogijo area of Ogun State, said on Saturday that armed men invaded the town late Friday and shot indiscriminately at residents, Xinhua news agency reported.The police have confirmed the attack but said findings were ongoing to further ascertain number of casualties.Ogun State police spokesman Muyiwa Adejobi said about 100 attackers brandishing various weapons reportedly stormed the community to wreak havoc, adding the invaders likely came from a riverine area in the state.The police spokesman said investigations were underway to ascertain the motive of the attack.