Amnesty International is greatly concerned by the continuing threat to the life of Alan Johnston, the BBC News reporter who has been missing for more than 100 days since his abduction in Gaza City on 12 March.

The human rights organisation is making a renewed appeal to his captors to release Mr Johnston immediately and is calling on both Palestinian Authority President Mahmoud Abbas and the leaders of Hamas - who currently exercise control over Gaza - to redouble their efforts to obtain his safe release.

Amnesty International’s new call comes after his kidnappers - the “Army of Islam” - released a video showing Mr Johnston wearing what he described in the film as an explosive belt. He said that his captors had threatened to detonate the belt if the hideout where he is being held is stormed to force his release.

Alan Johnston states in the video: "The situation now is very serious. As you can see I have been dressed in what is an explosive belt, which the kidnappers say will be detonated if there was any attempt to storm this area.”

He added: "Captors tell me that very promising negotiations were ruined when the Hamas movement and the British government decided to press for a military solution to this kidnapping."

It is believed that the release of the video may be in response to an ultimatum issued by the recently deposed Palestinian Prime Minister Isma’il Haniyeh, whose Hamas party remains in de-facto control of Gaza. Earlier in the day Isma’il Haniyeh had said in a speech: "We will not allow the continuation of the abduction of the British journalist. The issue of Alan Johnston must end."

Hostage taking is a grave violation of international law and can never be justified. Amnesty International urges the abductors of Alan Johnston to release him immediately.