Iraqi militants holding four western hostages have threatened to kill them unless all prisoners held by the Iraqi Government and US forces are freed by next Thursday
A group called the Swords of Truth Brigade issued the ultimatum in a videotape broadcast on the Arabic television station, al-Jazeera.
An envoy seeking to secure the men's release has arrived in Baghdad.
Among those being held is the British peace campaigner, Norman Kember.
Mr Kember, 74, was abducted a week ago in Baghdad while working with the Canadian-based organisation, Christian Peacemaker Teams.
He was kidnapped along with US citizen Tom Fox, 54, and two Canadians, James Loney, 41, and Harmeet Singh Sooden, 32.
The Canadian Prime Minister, Paul Martin, has condemned the threats as a 'callous act of terror against innocent people'.
19 Iraqi soldiers killed in ambush
At least 19 Iraqi soldiers have been killed following a bomb attack and ambush north of Baghdad.
The attack occurred in Adhaim, a volatile town just north of Baquba, about 100km from Baghdad.
The soldiers were travelling in a five-vehicle patrol when a bomb went off nearby. Immediately afterwards, guerrillas opened fire in what police described as a carefully executed plan.
Four military vehicles were destroyed in the assault and five civilians were wounded.
US military confirms media influence
The US military has confirmed that it paid to place stories in Iraqi newspapers.
But it has insisted that such 'information operations' were an essential tool for commanders to ensure the Iraqi population has 'current, truthful and reliable' information.
The US military said it was reviewing allegations raised in news reports about the program and will investigate any improprieties.
The disclosure of the practice of paying to plant favourable stories in the Iraqi press has been widely criticised as a blow to US credibility and to the independence of the Iraqi media.
US Senator John Warner has said the Pentagon is still gathering information on the extent of the secret program.
Mr Warner said the stories were put together by a group working directly under Lieutenant General John Vines, the second ranking commander in Iraq.
