Islamic extremists killed at least 25 fishermen during an attack in northeastern Nigeria’s Borno state, the police told The Associated Press on Thursday,

The rebels attacked the fishermen in the remote Mukdolo village of Borno where the years-long extremist violence is concentrated, said the local police chief Abdu Umar. Some of the bodies in the Wednesday attack were recovered and buried on Thursday, he said.

“There is no single human being in that place because it has been abandoned but the villagers from Dikwa go there to fish. Unfortunately, this time, Boko Haram (extremists) surrounded the place and killed 25 of them and nine escaped,” the police chief said of the attack. Locals reported more than 30 killed in the attack.

Nigeria, Africa’s most populous country and largest economy, continues to grapple with a 14-year-old insurgency in the northeast by Islamic extremist rebels of Boko Haram and its offshoot, the Islamic State West Africa Province. The extremists are fighting to establish Shariah law and to stop Western education.

More than 35,000 people have died and over 2 million have been displaced by the extremist violence, according to the U.N. Development Program.

Abba Modu with the local security outfit in Borno said the latest attack on Wednesday occurred after the rebels warned locals to stay off the river in the Mukdolo village which is near Sambisa forest, a popular hideout for the militants.

“The Boko Haram people said they now own the river, and no villager would be allowed to fish there except their members,” said Modu.