AKIPRESS.COM - The leader of an Islamist militant group which has abducted hundreds of Nigerian schoolgirls vowed to sell them as sex slaves despite international outrage at the kidnappings, media report.

Abubakar Shekau, the head of Nigerian extremists Boko Haram, said he would 'sell on the market' more than 270 girls captured by his fighters last month.

The group – whose name means 'western education is forbidden' – snatched the children during a raid in the village of Chibok in northeast Nigeria last month, AFP reported citing a video it had obtained.

In the video, Shekau declares: 'I abducted your girls. I will sell them in the market, by Allah.'

He is seen dressed in combat fatigues standing in front of an armoured personnel carrier and two pick-up trucks mounted with sub-machine guns.

His message comes after former British Prime Minister Gordon Brown, who is now a UN special envoy on education, led calls for Western governments including Britain to assist with their rescue.

A Foreign Office spokesman said the British government is in talks with their Nigerian couinterparts and 'security services' but declined to say if that might include special forces such as the SAS.  US Secretary of State John Kerry over the weekend also promised help.

In the latest video, the images are blurry at times, but zoom in to Shekau, who speaks in the local Hausa language and Arabic as well as English. Six armed men stand beside him with their faces covered.