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The UN Security Council has strongly condemned the abduction of hundreds of Nigerian schoolgirls, as the world body's secretary general dispatched an envoy to help find them.
The diplomatic moves came after Amnesty International said that Nigeria's military had been warned of an attack on a school in which more than 200 girls were abducted by Boko Haram Islamists three weeks ago, but failed to act for nearly five hours.
The Nigerian military denied the allegation.
At least 10 army search teams were trying to track down the girls in the remote far northeast, border guards were on high alert and the air force had so far flown at least 250 sorties.
Nigeria is keen to demonstrate that it is finally acting to trace the 223 girls still missing, after the teenagers' families accused them of inaction and indifference.
The unanimous UN Security Council declaration yesterday said the mass kidnappings "may amount to crimes against humanity" under international law, but made no explicit reference to charges in the International Criminal Court.
The 15 members of the council said they would follow the situation and consider "appropriate measures" to take against Boko Haram.
Meanwhile, UN Secretary General Ban Ki-moon announced he was sending his special representative for West Africa, Said Djinnit, to Abuja to discuss ways of helping authorities locate the girls.
US, British and French experts have already arrived on the ground to help trace the schoolgirls.
Hundreds of people from the girls' home town of Chibok, in northeastern Borno state, took to the streets of the state capital, Maiduguri, to vent their frustrations at the lack of immediate action.
At the same time, Nelson Mandela's widow Graca Machel broke her customary mourning period to plead for the girls' safe return.
Up to 200 armed Boko Haram fighters eventually abducted 276 girls after fighting a small number of police and soldiers stationed in the town.
