Esther Yakubu, mother of one of the kidnapped schoolgirls, cries after seeing her daughter Dorcas in a video released by Boko Haram. (Olamikan Gbemiga/AP)

Nigerian militant group Boko Haram has published a video apparently showing recent footage of dozens of schoolgirls kidnapped two years ago and saying some of them have been killed in airstrikes.

The Islamist group seized more than 270 girls from their school in Chibok, northeast Nigeria, in April 2014, part of an insurgency that began in 2009 and has killed about 15,000 people.

Dozens of the girls managed to flee to safety in the initial melee, but more than 200 are still missing.

In the video, which was published on social media, a masked man stands behind dozens of girls.

“We want to send this message first to the parents of these girls for them to know that these girls are still with us, some of them, and secondly they should tell the federal government of Nigeria to, with immediate effect, release our imprisoned brothers,” the man said.

“Some of the girls, about 40 of them, with God’s permission have been married. Some of them have died as a result of bombing by the infidels,” he said.

One veiled girl could be seen holding a baby. Parents have accused Boko Haram of having married off some of the girls against their will.

At the end of the video, unidentified bodies can be seen on the ground.

“Military jets have killed some of the girls,” said one of the girls, who was identified by Yakubu Kabu as his daughter Dorcas.

“When I heard her voice, I realize she is my daughter,” he told reporters in Abuja. “We are pleading with the government to help.”

Information Minister Alhaji Lai Mohammed said the government was “on top of the situation” to free the girls.

“Since this is not the first time we have been contacted over the issue, we want to be doubly sure that those we are in touch with are who they claim to be,” he said.

Army spokesman Rabe Abubakar was quoted as saying by PR Nigeria, an official news agency, that the military disputed the claims that the air force had hit the girls.

Authorities said in May that one of the missing girls had been found, and President Muhammadu Buhari vowed to rescue the others.

Boko Haram, which last year pledged loyalty to the Islamic State militant group, has kidnapped hundreds of men, women and children.

Under Buhari’s command and aided by Nigeria’s neighbors, the army has recaptured most territory once lost to Boko Haram, but the group still regularly stages suicide bombings.