The U.N. Security Council is strongly condemning attacks by the Islamic extremist group Boko Haram and expressing alarm at its links to the Islamic State group ahead of a summit this weekend in Nigeria to evaluate the campaign to combat the extremists.

A presidential statement approved Friday by the 15-member council demands that Boko Haram "immediately and unequivocally cease all violence and all abuses of human rights and violations of international humanitarian law." It also demands the immediate release of thousands of people held captive by Boko Haram including 219 Nigerian schoolgirls abducted in April 2014.

The council welcomed Nigerian President Muhammadu Buhari's "crucial initiative" to convene Saturday's summit in the capital Abuja to evaluate the regional response to Boko Haram.

U.S.-backed African governments have made advances against the group.