IRAQI gunmen holding an American hostage threatened last night to kill him unless US forces ended the siege of Falluja, where 450 civilians were reported to have died in heavy fighting last week.

The Arab television station, Al-Jazeera, broadcast a videotape of the captive looking shocked and exhausted 24 hours after he was seized in an attack on a US convoy between Falluja and Baghdad.

The middle-aged man, who was filmed in front of an Iraqi flag, was said to be a civilian contractor working for the American military. He identified himself as Thomas Hamill and said he was being well treated by his kidnappers. They had given him medical assistance for an arm wound, he said.

However, a spokesman for the captors said off camera that US troops must end their action at Falluja, where four American civilians were burnt and mutilated by a mob last week.

“Our only demand is to remove the siege from the city of mosques,” he said. “If you don’t respond within 12 hours . . . he will be treated worse than those who were killed and burnt in Falluja.”

The same station claimed earlier that three Japanese civilians — two aid workers and a photographer — captured earlier in the week would be freed this morning. Al-Jazeera said their kidnappers, who had threatened to kill them, had responded to a call by the Muslim Clerics Association.

However, two members of German special forces who had been missing since Wednesday were reported to have died in a gun battle. The men, Thomas Ritrath, 25, and Thomas Haffenker, 38, were members of the elite GSG-9 counter-terrorism unit. They disappeared after the six-vehicle convoy in which they were travelling came under attack.

Armed rebels showed a blood-caked body to Lee Gordon, a freelance journalist, who said he had seen a German identification badge in the victim’s wallet. He described how a teenager had been sharply rebuked by his commander for posing with one foot on the body.

There was continuing concern over the fate of a Briton who vanished in the city of Nasiriya six days ago. Gary Teeley, 37, a married man from Cambridgeshire with five children, was working as a consultant to a laundry contractor.

The spate of kidnappings provides a grim backdrop to a visit by Tony Blair to Washington on Friday. The prime minister will press President George W Bush for a diplomatic offensive in Europe to secure support for urgent measures to deal with the escalating crisis in Iraq.

Blair is to propose a tour of European capitals by Condoleezza Rice, Bush’s national security adviser, or Colin Powell, secretary of state. They are seen as the most likely figures in the Washington administration to win over critics of America’s tactics in Iraq, which senior figures in London described last week as heavy-handed. Blair wants international agreement on an enhanced United Nations role in supervising the handover of power to the Iraqis on June 30 and in organising elections to follow.

In further violence yesterday the US army killed 12 insurgents in a truck in northern Iraq. A senior Iraqi Red Crescent official and his wife were shot dead in their car in a separate incident.

Youths armed with rifles and grenade launchers fought American troops in a Sunni Muslim area of Baghdad, and shooting and mortar fire continued in Falluja, although Iraqi leaders were reported to have agreed a brief truce with the Americans. A US spokesman said five foreign fighters from Egypt, Syria and Sudan were among 60 guerrillas detained there.

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