President Barack Obama has vowed the US will do "everything we can" to help Nigeria in its search for the more than 200 kidnapped schoolgirls.
"This is a terrible situation," he told NBC's Today programme. "Boka Haram, this terrorist organisation that's been operating in Nigeria, has been killing people and innocent civilians for a very long time."
"We've always identified them as one of the worst local or regional terrorist organizations there is out there. And I can only imagine what the parents are going through," Obama said.