Alan Johnston has been held since 12 March

New Johnston video

In the tape, Mr Johnston says his captors have said they will detonate the vest if force is used to try to free him.

It is the second video released since Mr Johnston was abducted from a Gaza street on 12 March.

The BBC renewed its appeal for Mr Johnston's immediate release.

"It is very distressing for Alan's family and colleagues to see him being threatened in this way," a BBC statement said.

"We ask those holding Alan to avoid him being harmed by releasing him immediately.

"We are keeping his family fully informed and offering them our continued support."

Mr Johnston's father, Graham, said: "My family and I are obviously most concerned and distressed at this latest development.

"Our thoughts, of course, are with Alan in his present predicament. We earnestly request his abductors to release Alan, unharmed in any way."

Talks 'promising'

In the tape, posted on a website used by militants, Mr Johnston is seen wearing a device around his torso and attached to shoulder straps.

We will not allow the continuation of the abduction of the British journalist

Ismail Haniya

Hamas leader in Gaza

Mr Johnston appeals for a peaceful resolution to his situation, saying talks had reached an advanced stage.

"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."

HAVE YOUR SAY I can't face watching the latest video. It's both that it would seem wrong to be a spectator, but also that I'm too much of a coward to let my mind go there

Glyn Jones, North Harrow, UK

Send your message for Alan

"We will not allow the continuation of the abduction of the British journalist. The issue of Alan Johnston must end," he said in a speech to his supporters.

The British Foreign Office said it deplored such footage of Alan Johnston.

"We condemn the continued release of videos like this which can only add to the distress of Alan Johnston's family and friends," a spokeswoman said.

"They have not seen Alan for over 14 weeks. Those holding Alan should release him."

Mr Johnston was abducted by a group calling itself The Army of Islam.

A video was released on 1 June by the previously unknown radical Islamist group, in which the correspondent said he was in good health and was being treated well.

The Army of Islam has demanded the release of Abu Qatada, a Palestinian-born Islamic cleric who is suspected of having close links with al-Qaeda and is held by the UK government as a threat to national security.

Mr Johnston, from Scotland, was the only Western reporter permanently based in Gaza and his abduction has triggered appeals for his release from lawmakers and human rights groups around the world.

More than 170,000 people have signed an online petition calling for his release.

Text of latest Alan Johnston video:

"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, and the situation is now very serious.

"As you can see, I've been dressed in what is an explosive belt, which the kidnappers say will be detonated if there is any attempt to storm this area. They say they're ready to turn the hideout into what they describe as a death zone if there is an attempt to free me by force.

"I do appeal to the Hamas movement and the British government not to resort to the tactics of force in an effort to end this. I would ask the BBC and anyone in Britain who wishes me well to support me in that appeal. It seems the answer is to return to negotiations, which, I am told, are very close to achieving a deal."