Parents anxious for release of only Dapchi schoolgirl still held by Boko Haram

The police officer's heart races anytime his phone rings.

He told CNN that he's expecting to hear news that his 15-year-old-daughter Leah Sharibu, has been set free by Boko Haram.

Leah is believed to be the only schoolgirl still in Boko Haram captivity after the group last Wednesday released 107 students that its militants snatched from a boarding school in Dapchi, a town in Nigeria's Yobe state.

Nathan said his family has been thrown into despair since last Wednesday. The freed girls told him his daughter was left behind because she refused to renounce her Christian faith.

The aggrieved father urged the Nigerian government and international community to mount pressure on the terror group to release his daughter.

"I am just praying right now that they release her," he told CNN Tuesday.

"I hope government and everyone will not give up on her. They will pressure Boko Haram to let her go."

Leah's mother said it's become more difficult for her to see other families reunited with their daughters who were also taken in the February 19 raid.

"I am happy others are back, but what of mine?" Rebecca Sharibu asked.

"I haven't heard anything about my daughter's release," she told CNN.

Nigeria President Muhammadu Buhari promised last week that Leah would not be abandoned with the militants.

The government was also negotiating a ceasefire with the group, the country's information minister, Lai Mohammed, said Sunday.

Boko Haram came to the world's attention after sparking outrage four years ago following the kidnapping of nearly 300 schoolgirls from a boarding school in Chibok in Borno state.

The group released 82 of the girls in exchange for the release of five of its members last year. The whereabouts of more than 100 Chibok girls remain unknown.