Amnesty International is accusing the Nigerian army of killing hundreds of people belonging to a minor sect of Shi'ite Islam in December, Reuters reports. The military denies the claims, saying that the organization is biased.

According to the army, a member of the Islamic Movement tried to assassinate the chief of staff last December. The next day, the military carried out raids on several buildings belonging to Islamic Movement members.

Amnesty International says that over 350 people were illegally killed during these few days, and offered satellite pictures that it says depict a mass grave.