Boko Haram gunmen attacked an island on the Niger side of Lake Chad, with locals reporting heavy casualties among those who fled but no official confirmation of the death toll.

Boko Haram gunmen attacked an island on the Niger side of Lake Chad, with locals reporting heavy casualties among those who fled but no official confirmation of the death toll.

A private radio station in Niger said that two people died in a fire in the remote village on Sunday evening but one survivor spoken to by AFP said the death toll was higher.

"A lot of people jumped into the lake to escape the attack. I think that a lot of people drowned, in particular women and children," said one man, who escaped with his family in a boat.

Abubakar Gamandi, the head of the fishermen's union in Borno state, northeast Nigeria, said he received phone calls from members telling him about the attack, which happened on Sunday.

"No one knows how many people died in the attack but many residents fell in the lake and are believed to have drowned," he said.

The attack began at about 7:00 pm (1800 GMT) on Sunday, the survivor and Gamandi said, both blaming the Islamist group, which has been waging an insurgency in northeast Nigeria since 2009.

"We had just finished evening prayers when the attackers arrived in a speed boat. They started to fire on the village and throw explosives at our houses," said the man, who asked not to be named.

Two humanitarian workers in the area confirmed the attack but did not have more details, while a local lawmaker said that the Niger army was not present in the area.