As the weeks stretch into months since her 18-year-old daughter Hauwa was kidnapped with 275 other schoolgirls by Islamist militants in the Nigerian town of Chibok, Rahila Musa Bitrus fasts and prays for her safe return.

"I haven't given up, but it's obvious that the government needs to step up their rescue operation so that our girls can be returned to us," Bitrus, 41, said by phone from Chibok. "It's so painful and sad."

Hope for the secondary schoolgirls' freedom is fading. While Nigeria's military said in May it knows where they are and last month arrested a Boko Haram cell leader involved in their abduction, the U.S., which is aiding the rescue effort with surveillance aircraft, said their location remains unknown.