People take part in a protest demanding the release of abducted secondary school girls from the remote village of Chibok, in Lagos May 5, 2014. The Islamist militant group Boko Haram claimed responsibility on Monday for the abduction of more than 200 schoolgirls during a raid in the village of Chibok in northeast Nigeria last month, the French news agency AFP reported, citing a video it had obtained. Boko Haram on April 14 stormed an all-girl secondary school in Chibok, in Borno state, then packed the teenagers, who had been taking exams, onto trucks and disappeared into a remote area along the border with Cameroon. [Photo/Agencies]

Boko Haram militants stormed an all-girl secondary school in the village of Chibok, in Borno state, on April 14 and packed the teenagers, who had been taking exams, onto trucks and disappeared into a remote area along the border with Cameroon.

The attack shocked Nigerians, who have been growing accustomed to hearing about atrocities in an increasingly bloody five-year-old Islamist insurgency in the north.

"I abducted your girls. I will sell them in the market, by Allah," Boko Haram leader Abubakar Shekau says in a video, chuckling as he stands in front of an armoured personnel carrier with two masked militants wielding AK-47s on either side of him.

"Allah has instructed me to sell them. They are his property and I will carry out his instructions," he says.

Boko Haram, seen as the main security threat to Nigeria, Africa's leading energy producer, is growing bolder and extending its reach. The kidnapping occurred on the day a bomb blast, also blamed on Boko Haram, killed 75 people on the edge of Abuja, the first attack on the capital in two years.

The group's name means "Western education is sinful" and Shekau in the video makes reference to the fact that the girls were undergoing Western education.

The militants, who say they are fighting to reinstate a medieval Islamic caliphate in northern Nigeria, carried out a second bomb attack more than two weeks later in the same area, killing 19 people and wounding 34 in the suburb of Nyanya.

The girls' abduction has been hugely embarrassing for the government and threatens to overshadow its first hosting of the World Economic Forum (WEF) for Africa on May 7-9.

Nigerian officials had hoped the event would highlight their country's potential as an investment destination since it became Africa's biggest economy after a GDP recalculation in March.

PROTESTER DETAINED, THEN FREED

The apparent powerlessness of the military to prevent the attack or find the girls in three weeks has led to protests in the northeast and in Abuja and Lagos.

On Sunday, authorities arrested a leader of a protest staged last week in Abuja that had called on them to do more to find the girls, further fuelling outrage against the security forces.

Naomi Mutah Nyadar was picked up by police after a meeting she and other campaigners held with President Goodluck Jonathan's wife, Patience, concerning the girls.

Nyadar was taken to Asokoro police station, near the presidential villa, said fellow protester Lawan Abana, whose two nieces are among the abductees. She was released later on Monday and police said she had merely been invited in for an interview.

A presidency source said Nyadar had been detained because she had falsely claimed to be the mother of one of the missing girls. Abana said she had made no such claim.