MAIDUGURI, Nigeria :  The Nigerian schoolgirls kidnapped by Boko Haram were taken to a stronghold of the militant group, parents said Wednesday, as the security forces pressed on with a search to find the hostages.

The mass abduction of more than 100 girls by gunmen in the northeastern state of Borno late Monday came just hours after a bomb ripped through a packed bus station on the outskirts of Abuja, killing 75 people, the deadliest attack ever in the capital. The bombing was also blamed on Boko Haram, a group whose five-year extremist uprising has shaken Africa’s most populous country and top economy.

Three girls who escaped and returned to Borno’s Chibok area briefed locals about the attack at the home of the area’s tribal chief on Wednesday, said Lawal Zanna, whose daughter was among those abducted.

“The girls told us they were taken to the Konduga district part of Sambisa forest by their captors,” said Zanna, referring to an area where Boko Haram is known to have well-fortified camps.

His account was supported by two other Chibok residents who asked that their names be withheld.

The girls said they ran after getting permission from the gunmen to use the bathroom and were helped back to Chibok by nomadic herdsmen from the Fulani ethnic group.

“My daughter is not among the three lucky girls but their escape and the news on the whereabout of the other girls has given me more hope,” Zanna told AFP.

Borno’s Governor Kashim Shettima told journalists that 14 of the hostages had escaped so far and offered 50 million naira ($300,000, 215,000 euros) to anyone with information that leads to the others being rescued.

The gunmen stormed the Government Girls Secondary School after sundown, torching several buildings before opening fire on security forces guarding the school.

Boko Haram, whose name means “Western education is forbidden”, has repeatedly attacked schools and universities in an insurgency that has killed thousands of people since 2009.

Intensifying violence in the group’s northeastern base has forced school closures across the region, including at Chibok, but the girls were reportedly told to return this week to write end-of-term exams.

Witnesses said the gunmen killed a police officer and soldier in the shootout and ultimately forced their way into the school.

They then forced the girls outside and loaded them onto trucks and drove off into the bush of the remote region.

Some of the girls escaped by jumping off a truck when the gunmen became distracted by a vehicle that had broken down.

“Our security services are on a manhunt for the girls,” Information Minister Labaran Maku told journalists in Abuja.

Senator Ali Ndume, who represents the region, said the pursuit included soldiers backed by members of a local vigilante force which formed last year to help fight Boko Haram.

“They are now combing the forest to rescue the schoolgirls,” he told AFP. “They are being aided by surveillance helicopters,” he said, but noted the difficulty of the search in a vast forest that extends to neighbouring Cameroon.

The United Nations children’s organisation (UNICEF) condemned the attack “in the strongest possible terms”, and urged Nigeria “to urgently take steps to make sure that the children are returned to their families”.

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Nigerian President Goodluck Jonathan and the military have sought to portray Boko Haram as rapidly losing strength thanks to a massive offensive in the northeast launched last May.

Jonathan has faced mounting criticism over his failure to stem the violence and protect the defenceless civilians who have been among Boko Haram’s prefered targets, even as he has seeks to portray Nigeria as a country on the rise.

The information minister characterised Boko Haram’s uprising as uniquely gruesome.

“Kidnapping young children is exactly what makes this group of terrorists in Nigeria among the worst in the world,” Maku said.