Hundreds of people, including women and children, have been killed in a revenge attack after religious clashes near the Nigerian city of Jos.
Local officials say three mainly Christian villages near Jos were attacked from nearby hills by people with machetes.
Some reports put the number of dead at more than 500.
In January, Jos was put under a military curfew after violence between Christians and Muslims in which at least 200 people were killed and thousands displaced.
Nigeria's acting president Goodluck Jonathon has sacked the country's national security advisor in the wake of the outbreak of violence, and has put security forces on alert to stop the flow of weapons to the area.
Many of the dead in the villages of Zot and Dogo-Nahawa are reported to be women and children.
Mark Lipdo from the Christian charity Stefanus Foundation says the village of Zot has been almost wiped out.
The authorities say the villages are now calm after troops and military vehicles entered them.
The United Nations, the US Secretary of State and the Vatican are all urging Nigerians to exercise restraint but observers say the massacre is likely to push the country further into crisis.