GAZA CITY, Gaza Strip – In a video released Monday, a kidnapped British journalist appears with what he says are explosives strapped to his body and warns that his captors intend to set them off if rescuers attempt to free him by force.

The tape of Alan Johnston, called “Alan’s Appeal,” was put on a Web site used in the past by militant groups to post messages. It was made by the Army of Islam, a shadowy group that claimed responsibility for snatching Johnston, a correspondent with the British Broadcasting Corp., from a Gaza City street on March 12.

“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,” Johnston says in the 1 minute, 42 second, recording, looking nervous and under stress. “And the situation is now very serious, as you can see.”

Hamas militants on Monday released a recorded message from Cpl. Gilad Shalit, the Israeli serviceman captured near the border with Gaza a year ago. It was the first sign of life from the young serviceman since his seizure.

In the audio message, posted on the Web site of Hamas’ military wing, Shalit expressed disappointment in the “lack of interest” of the Israeli government in his fate. Negotiations for Shalit’s release, mediated by Egypt, have repeatedly broken down and been complicated since Hamas took control of Gaza two weeks ago.

No video of Shalit was posted on the Web site.

In the video of Johnston, on another site, the journalist is wearing a blue and white checked vest.

“I have been dressed in what is an explosive belt, which the kidnappers say will be detonated if there is an attempt to storm the area,” he continued. “They say they are ready to turn the hideout into what they describe as a death zone if there is an attempt to free me by force.”

Johnston stood and shook his head as he spoke. Light entered the room from above, and Arabic subtitles were shown on the screen.

“I do appeal to the Hamas movement and the British government not, not to, resort to the tactics of force in an effort to end this,” he said, in a jittery tone.

“I’d ask the BBC and anyone in Britain who wishes me well to support me in that appeal,” he said. “It seems the answer is to return to negotiations, which I am told are very close to achieving a deal.”

Neither the British government nor the BBC have publicly advocated the use of force to free Johnston.

A BBC statement released on Monday reiterated calls for his peaceful release.

“We are aware of the video and its contents,” the statement said. “We ask those holding Alan to avoid him being harmed by releasing him immediately.”

A spokeswoman for the British Foreign Office condemned the release of the video, while Johnston’s father, Graham Johnston, said his family was “most concerned and distressed at this latest development” and pleaded for Alan to be freed unharmed.

Since violently taking control of the Gaza Strip this month, Hamas has said it would seek the release of Johnston – an apparent bid to gain favor with the West. An attempt to secure Johnston’s release fell through last Monday, said Mahmoud Zahar, a hardline Hamas leader involved in negotiations.

“We are moving many channels to try release the kidnapped journalist,” deposed Prime Minister Ismail Haniyeh of Hamas said at a meeting on Monday.

While the Army of Islam has demanded the release of an al-Qaida militant imprisoned in Britain, analysts believe Mumtaz Doghmush, the Palestinian group’s leader, wants to guarantee his large, heavily armed clan is not disarmed if Johnston is freed.

Hamas has vowed to disarm Gaza’s large tribes in its effort to quell anarchy in the Strip. But the Doghmush clan has running blood feuds with at least three other Gaza tribes, and disarming would leave the clan defenseless.

“If Mumtaz gives up Alan, he’s a dead man and he knows it. If Hamas doesn’t kill him, another tribe wanting revenge will,” said an analyst close to the family. He declined to be identified, fearing for his safety.

The Web site where the video appears is called Falluja of Iraq. It has been used by militant groups in the past. The only other video recording of Johnston was posted on a different Web site on June 1.

Johnston was the last Western correspondent based in Gaza. Others left because of the security situation and a wave of kidnappings.