The U.N. Security Council is condemning the recent escalation of attacks by the Nigerian extremist group Boko Haram in the strongest terms and expressing deep concern that its activities are undermining peace and stability in central and West Africa.

The presidential statement approved Monday was the council's first formal reaction to Boko Haram's activities, which have increased in ferocity.

It comes on the eve of Tuesday's meeting in Niger's capital, Niamey, to discuss regional military action to respond to the threat posed by the Islamic militant group.

The council demanded that Boko Haram immediately halt all hostilities and demobilize. It demanded the immediate release of all those abducted including the 276 schoolgirls seized in April.

It warned that some acts by Boko Haram "may account to crimes against humanity."