Nigerian soldiers and vigilantes are hunting "around the clock" for the Islamist fighters holding scores of schoolgirls hostage, an official said Monday, as locals claimed the number kidnapped was far higher than first reported.
The mass abduction blamed on Boko Haram militants in northeastern Borno state has been described as one of the most shocking attacks in the group's five-year extremist insurgency.
Borno's government has said 129 students were taken from the Government Girls Secondary School in Chibok when gunmen stormed the town under the cover of darkness on April 14.
Isa Gusau, a spokesman for Borno's Governor Kashim Shettima, said that 52 had escaped so far, after seven more girls were found safe on Monday.
Two ran to the state capital Maiduguri, while five others found their way home, he said.
"With this development, we now have 77 girls still in the custody of their abductors," Gusau told AFP.
"This is the most trying moment Governor Shettima has faced in the last three years," he said.
"A security (operation) has been put in place to rescue the remaining girls," he told AFP, saying this included soldiers and members of a civilian force that formed last year to help the military fight Boko Haram.
"We are working around the clock to ensure all of them are freed unharmed," he said.
- Figures disputed -
Gusau's figures were disputed Monday by the school's principal, Asabe Kwambura, who said she was working with parents to compile a complete registry of those taken.
"A total of 230 names" were registered by parents, she said.
"So far, 43 girls have escaped on their own. We still have 187 missing."
Officials in Borno did not answer calls and text messages seeking clarification on the principal's figures.
- Plea for mercy -
Locals re-issued a plea to Boko Haram to show mercy, but the Islamists, blamed for killing thousands across the region, have so far not commented on the abductions.
The group's name translates as "Western education is forbidden," and the militants have repeatedly attacked schools and universities during an uprising aimed at creating a strict Islamic state in northern Nigeria.
Students have been massacred while sleeping in their dormitories, but a mass kidnapping specifically targeting girls is unprecedented and has been condemned worldwide.
"We are appealing to Boko Haram to show mercy and release these girls," said Chibok resident Haladu Sule.
"The people of Chibok... will know no peace until they are freed."
Locals have fiercely criticised the rescue mission, claiming they have not yet seen a large build-up of troops in the region or any indication that the military had mobilised a major search effort.
Some of the girls who escaped have said the Islamists took the hostages to Borno's Sambisa Forest area, where Boko Haram is known to have well-fortified camps.
Parents have trekked through the bushlands of the remote region in a desperate search for their daughters, pooling money to buy fuel for motorcycles and cars.
Some turned back after being warned that the Islamists were nearby and prepared to slaughter anyone who advanced further.
The kidnapping came hours after the deadliest attack ever in Nigeria's capital, a bomb blast at a crowded bus station that killed at least 75 people.
Boko Haram's leader Abubakar Shekau has claimed responsibility for that attack.
In an Easter message, President Goodluck Jonathan said Nigeria will "overcome" the Islamist threat.
"God willing, we must bring Boko Haram to an end."