An Islamic group that claims to be holding kidnapped BBC correspondent Alan Johnston has sent a videotape of demands to the al-Jazeera Arabic news channel.

The videotape, which was sent to al-Jazeera in Gaza, contains no new photos of Johnston but it shows a photo of his BBC identification card.

It also contains a demand for the release of Muslim prisoners being held in British prisons and the release of a specific prisoner. The group, which calls itself Army of Islam, or Jaish al Islam, made the tape, the authenticity of which could not be verified.

Johnston, 44, was kidnapped at gunpoint on March 12 near his Gaza city home.

Johnston, the only Western journalist living in Gaza, has not been seen or heard from since. He had worked in Gaza for three years.

The BBC responded to the release of the videotape with a statement saying it would investigate but not comment and that Johnston should be released immediately.

"We are aware of the tape released by the Army of Islam concerning our Gaza correspondent, Alan Johnston. We have no comment on the demands made of the British government in the tape — we remain concerned for Alan's well-being and call for his immediate release," said the BBC statement on its website.

According to a report on the al-Jazeera website, the group says on the tape: "We demand from Britain that it release our prisoners and particularly Sheikh Abu Qatada the Palestinian and in this regard we do not forget our prisoners in other infidel countries and we say to all of them free our prisoners or we will do the same to you.

"We won't make an exception for anyone. If you need money to release our prisoners we will give you all you need up to the last dirham we have."

BBC reported that Abu Qatada is an Islamic cleric born in the Palestinian territories and that he is being held by the British government because he is considered a threat to national security. He is suspected of having ties to the militant group al-Qaeda.

Mark Klusener, news editor at Middle East Eyewitness News, told CBC News from the city of Ramallah on the West Bank on Wednesday that the tape is the first real list of demands in connection with the kidnapping.

"At this stage, the BBC hasn't verified it," he said.

Klusener said the group was practically unknown in Gaza until a year ago. It gained prominence by joining other groups in the kidnapping of Cpl. Gilad Shalit. The Israeli soldier was abducted in June 2006 during an attack on a southern Israeli military post. 

He said the group is believed to be a small armed group that is a splinter group of the Popular Resistance Committee, which calls for the elimination of Israel and the creation of an Islamic state. It is influenced by al-Qaeda, but it is not affiliated with the militant group, he added.

About three weeks ago, a previously unknown militant group claimed to have killed Johnson, but the Palestinian Authority said it thought the journalist was still alive.

The group calling itself the Al Tawhid Al Jihad brigade said it had killed Johnston to support demands for the release of Palestinian prisoners held by Israel. Its claim was never verified.

Klusener said the Palestinian Authority seems to know who exactly is holding Johnson and where he is being held but is reluctant to get involved and to launch a rescue operation out of fear it could jeopardize his safety.