KADUNA, Nigeria (Reuters) - Gunmen ambushed and killed at least 62 members of a volunteer vigilante group in Nigeria's northwestern Kebbi state, the head of the group and a police spokesman said, in the worst violence to hit the state since mid-January.

       Many northwestern states in Nigeria have groups of volunteers who help defend villages and towns from armed gangs as the security forces are stretched fighting Islamist militants and the gangs, known as bandits.

       Usman Sani, the head of the "Yan Sa Kai" vigilante group in Kebbi, told Reuters that his group had planned to attack bandits in the Sakaba area on Sunday night but someone tipped them off.

       "They lay in ambush, hid their motorcycles in the shrubs, circled us and opened fire from different directions," Sani, a retired soldier, said on Tuesday. He said 62 people had been killed.

       Kebbi police spokesman Nafiu Abubakar confirmed the ambush but said he did not have details on how many people had been killed.

       In January, dozens of gunmen on motorbikes ransacked a village and killed more than 50 people in Kebbi.

       Gunmen have spread terror across the northwest, where they have kidnapped hundreds of school children and villagers for ransom.

       The violence has compounded the problems in northern states, which are typically poorer than those in the south.

       (Editing by MacDonald Dzirutwe and Robert Birsel)