Boko Haram has released a new video claiming to show the missing Nigerian schoolgirls who were abducted last month, alleging they had converted to Islam and would not be released until all of its prisoners held by Nigeria were freed.

In the video, obtained by the AFP news agency on Monday, Abubakar Shekau, the group's leader, is shown speaking for 17 minutes before showing what he said were about 130 of the girls, wearing full-length abayas and praying in an undisclosed rural location.

Nearly 300 girls were abducted on April 14 from the northeastern town of Chibok, in Borno state, which has a sizeable Christian community. Fifty-three girls managed to escape.

Three of the girls in Monday's video are interviewed in the recording. Two say they were Christian and had converted while one said she was Muslim.

The girls appeared calm and one said that they had not been harmed.

There was no indication of when the video was taken, although the quality is better than on previous Boko Haram videos and at one point an armed man is seen in shot with a hand-held video camera.

Boko Haram has been waging an increasingly deadly insurgency in Nigeria's mainly Muslim north since 2009, attacking schools teaching a "Western" curriculum, churches and government targets.

Civilians have borne the brunt of recent violence, with more than 1,500 killed this year alone, while tens of thousands have been displaced after their homes and businesses were razed.

International help

Nigeria's government has been criticised for its lack of immediate response to the kidnapping but has been forced to act after Shekau threatened to sell the girls as slaves.

President Goodluck Jonathan has accepted help from the United States, Britain, France, China and Israel, which have sent specialist teams to help in the search effort.

In the video, Shekau appears in front of a lime green canvas backdrop wearing combat fatigues and carrying an automatic weapon. He does not appear in the same shot as the girls at any point.

Speaking in Hausa and Arabic, he restates his claim of responsibility made in a video released last Monday and said the girls had converted to Islam.

The rebel leader said that Boko Haram's "brothers in arms" had been held in prison for up to five years and suggested that the girls would be released if the fighters were freed.

"We will never release them until after you release our brethren," he said.

Boko Haram has made prisoner exchange demands before without success and Nigeria's government again dismissed the request outright.

Asked if the government would reject Shekau's suggestion, Interior Minister Abba Moro told the AFP: "Of course."

"The issue in question is not about Boko Haram... giving conditions," he added.

Boko Haram has kidnapped women and young girls in the past and Shekau indicated that more were being held.

Eleven girls were abducted from the Gwoza area of Borno state on May 4.

Source: Al Jazeera and agencies