Eight teenage girls have been allegedly kidnapped by Nigerian terror group Boko Haram, according to police and local media.

A police source, who could not be named, told Reuters the girls were taken away on trucks, along with looted livestock and food.

Lazarus Musa, a resident of Warabe in northern Nigeria, said: "They were many, and all of them carried guns. They came in two vehicles painted in army colour. They started shooting in our village".

Boko Haram group, which opposes the westernisation of Nigeria and seeks to impose Islamic sharia law in Africa's most populous nation, kidnapped nearly 300 girls on 14 April sparking global outrage.

About 50 of them managed to escape, but some 220 are still missing.

The girls, who were kidnapped while in school, are being allegedly sold as brides to militiamen and smuggled to neighbour countries Chad and Cameroon.

Boko Haram leader, Abubakar Shekau, released a video in which he taunted that the girls would be sold in the market place - as willed by Allah.

"I abducted your girls. I will sell them in the market, by Allah ... Allah has instructed me to sell them. They are his property and I will carry out his instructions".

The UN warned the militants that there was no statute of limitations if they carried out their leader's threat to sell the girls.

"We warn the perpetrators that there is an absolute prohibition against slavery and sexual slavery in international law. These can under certain circumstances constitute crimes against humanity," UN human rights spokesman Rupert Colville told a news briefing in Geneva.

The US said it will send FBI agents to help trace the girls.

Hundreds of protesters marched through the Nigerian capital of Abuja to press for the release of the schoolgirls.

Two Nigerian women were arrested after they took part in a protest aimed at criticising the government of President Goodluck Jonathan, accused of not doing enough to negotiate the release of the girls.

"Attention from the international media, galvanized by the Twitter hashtag #BringBackOurGirls, has apparently embarrassed the government, which this week is hosting in Abuja the World Economic Forum on Africa," Human Rights Watch said.

"The government responded to the pressure by setting up a committee to, among other things, articulate a framework for the rescue of the missing girls."