A commander of the Al Qaeda-linked Islamist group which kidnapped nearly 300 Christian girls from a school in Nigeria, has released a chilling video in which he mocks the victims and promises to sell them as slaves.

The man identifies himself as Abubakar Shekau, the leader of the Boko Haram terrorist group, and begins by dispelling any doubts about who was behind the kidnapping in April, boasting "I abducted your girls. I will sell them in the Market by Allah!"

Breaking into laughter he continues: "There is a market for selling humans. Allah says I should sell. He commands me to sell. I will sell women!"

Boko Haram has been responsible for scores of terrorist atrocities in Nigeria, usually against Christian and government targets, but also occasionally against Muslim figures who oppose them. The mass-kidnapping, which took place in April, was not the group's first attack on a school. Just two months previously the group shot and burned to death dozens of students in an attack on a boarding school.

In a similar attack in 2013, Boko Haram terrorists murdered 50 students as they slept in their dormitories. In July of that year 29 pupils and a teacher were burned alive in another school.

"Boko Haram" translates literally as "Western education is forbidden" in the Hausa language prominent in Nigeria's Muslim-majority north, reflecting the group's opposition to any non-Muslim or western influence in the country, including within its education system.

The attack last April in Chiboke, Borno state, in which the 276 girls were kidnapped also saw 16 people killed and many more wounded.

An international campaign has been set up in response to the atrocity, including a viral social media campaign under the hashtag #bringbackourgirls.