Large areas of Nigerian towns attacked by radicals were razed to the ground in a widespread campaign of destruction, according to satellite images released Thursday by Amnesty International.

Amnesty International said the detailed images of Baga and Doron Baga, taken before and after the attack earlier this month, show that more than 3,700 structures were damaged or completely destroyed.

The images were taken Jan. 2 and Jan. 7, Amnesty International said. Boko Haram fighters seized a military base in Baga on Jan. 3 and, according to witnesses, killed hundreds of civilians in the ensuing days.

Daniel Eyre, Nigeria researcher for the human rights group, said in a statement that the assault on the two towns was the largest and most destructive of all the Boko Haram assaults analyzed by Amnesty International.

The group said interviews with witnesses as well as local government officials and human rights activists suggest hundreds of civilians were shot; last week, the human rights group noted reports of as many as 2,000 dead. The Nigerian military has cited a figure of 150 dead, including slain rebels.

Nigeria’s home-grown Boko Haram group drew international condemnation when its fighters kidnapped 276 schoolgirls from a boarding school in northeast Chibok town last year. Dozens escaped but 219 remain missing. SAPA