The Islamist terror organisation Boko Haram has released a video showing kidnapped Nigerian schoolgirls. The girls shown in the 17-minute video posted on YouTube are wearing full veils and seen praying from an undisclosed location.

In the video, the purported head of the terrorist group, Abubakar Shekau, said the girls had converted to Islam and that they would be held until all the imprisoned militants are freed.

By press time, the Nigerian government was yet to react to the demands.

The girls were kidnapped on April 15 when Boko Haram invaded a boarding school in the North Eastern town of Chibok, Nigeria.

The attackers forced an estimated 276 girls into trucks, and drove off. Eight more were kidnapped days later.

Shekau had previously spoken about the abduction in other filmed messages, where he appeared in military fatigues flanked by armoured vehicles.

President Paul Kagame last week joined a global campaign in condemning the kidnapping of the school girls. The abduction has triggered a global and international push to rescue the girls using the Twitter hashtag #BringBackOurGirls.

Speaking to CNN’s Isha Sasay, President Kagame dubbed the abduction outrageous and unfortunate, and  urged external help  in finding the girls.

"This is an outrageous situation that should never have happened or should never happen anywhere. We feel with and for the Nigerian government and the people of Nigeria, especially the families that have to go through this and, of course, the girls that have been abducted,” Kagame said.

"One imagines the situation the girls are going through. This should never happen again. There is no reason justifying why this kind of thing should happen or ever happen,” he added.

Some sections of the media and international organisations have criticised the Nigerian government on how it has handled the situation but President Kagame said that rather than criticise the government, there should be concerted effort to find a solution to the problem.

"I do not find a place for criticism, especially at a point when we are faced with a situation like this. All we need is to to concentrate on finding a way to save the girls,” he said.

He added: "I guess the problem is multi-dimensional and bigger than meets the eye. There is, therefore, need for international assistance in finding a solution to the problem.”

There are concerns that the girls may now have been split up into a number of groups, and that some may have been smuggled out of the country.

Several countries have pledged to assist in the search for the missing girls and efforts include US hostage negotiators, counter-terror experts and intelligence agents from Britain, France, China, Spain and Israel.