A woman shouts during a vigil in Abuja calling for the release of Nigerian schoolgirls abducted by Boko Haram in the remote village of Chibok Reuters

Nigerian Boko Haram insurgents have killed at least 11 parents of the estimated 220 missing girls who were kidnapped in Chibok, Borno State, on 14 April.

The parents died before the abducted girls could be freed and reunited with their families.

According to an AP report, seven missing girls' fathers were among the 51 victims of Boko Haram's latest attack in Kautakari village, near Chibok.

Four other parents died due to heart failure, high blood pressure and other illnesses believed to be related to the trauma of the mass kidnapping.

"One father of two of the girls kidnapped just went into a kind of coma and kept repeating the names of his daughters, until life left him," Chibok community leader Pogu Bitrus said.

The news came as Nigerian president Goodluck Jonathan met with some relatives of the missing girls in Abuja, Nigeria's capital.

"We are very, very mindful of the safety of the girls. We want to return them all alive to their parents. If they are killed in any rescue effort, then we have achieved nothing," he said.

Damboa Nigeria map
Boko Haram is closing in on Chibok, attacking villages closer to the town. The terror group recently declared the hegemony of the Damboa town, which is 37 km from Chibok. Google maps

"We are doing everything humanly possible to get the girls out. This not the time for talking much. This is the time for action. We will get to the time that we will tell stories. We will get to the time that we will celebrate and I assure you that, by God's grace, that time will come soon."

Boko Haram – which translates from Hausa into 'Western education is forbidden' wants the imposition of sharia law in the country - is closing in on Chibok, attacking villages closer to the town.

The insurgents recently declared the hegemony of Damboa - a town 37 km from Chibok - after days of fighting that resulted in hundreds of people dead and more than 15,200 displaced.

In June, the terror group carried out deadly attacks in three villages surrounding Chibok, killing at least 54 people.

Boko Haram carries out its attacks primarily in northern Nigeria, where three states – Borno, Yobe and Adamawa - have been under a state of emergency since May.

After hundreds of protesters marched through the Nigerian capital of Abuja to press for the release of the schoolgirls, the government banned rallies in the capital, citing security concerns.

Chibok schoolgirls abduction factbox

The Islamist militants abducted the girls on 14 April.

About 50 of the kidnapped girls managed to escape, but some 220 are still missing.

The victims, aged between 16 and 18, are being allegedly smuggled to Cameroon and Chad and sold as brides to militants for 2,000 naira — £7. Others are being forced to marry their abductors.

Nigeria's former President Olusegun Obasanjo warned that many kidnapped girls will never return home, and only those who become pregnant in the forest have the best chance of being freed.