The wife of Norman Kember, a Briton kidnapped in Iraq, has made a televised appeal begging for his release.
Pat Kember said her husband was a very caring man who believed in peace and had come to Iraq to help its people.
Mr Kember, 74, from Pinner in north London, was kidnapped on Baghdad with three other westerners last week.
Mrs Kember's appeal was shown in a 30-second film by Arab broadcaster al-Jazeera. In it she said her husband and his friends were allies of Iraq.
"Throughout his life he bravely fought against all kinds of injustice," she said.
"He went to Iraq to help the Iraqi people to stop the spread of abuse and to understand the situation in order to make Iraq a safer place.
"Please release Norman and his colleagues so that they can continue their work for the sake of peace in Iraq.
"They are friends and allies who want to help you to overcome evil by engaging in a humanitarian action."
Last Friday the station broadcast a video in which the kidnappers threatened to kill Mr Kember and his colleagues by Thursday, unless all prisoners in US and Iraqi detention centres were released.
Mr Kember is being held with American Tom Fox, 54, and Canadians James Loney, 41, and Harmeet Singh Sooden, 32.
He had travelled to Iraq as a "gesture of solidarity" with Christian Peacemaker Teams (CPT), a Canada-based international peace group.
Meanwhile, an anti-war envoy is continuing to meet with Sunni Muslim groups in Iraq in a bid to secure the release of the four men.
Some have already called for their release and Iraq's largest Sunni party, the Iraqi Islamic party, said the kidnapping tarnished the image of Islam.
"The kidnapping will have a grave negative effect among those who call for ending occupation," it said.
Envoy Anas Altikriti was sent to Baghdad by the Muslim Association of Britain, Stop the War and CND.
He told the BBC that, as an Iraqi, he appreciated the country's predicament.
"It's a very very dangerous situation, there can be no question about it, but I come as an Iraqi, someone born in Iraq, and therefore, I'm at home," he said.
"And therefore I'm joining in, riding the same boat that 23, 24 million Iraqis have been in for the past two-and-a-half years and the very same situation that Mr Kember - quite nobly, him and his colleagues - accepted to enter themselves, in order to carry out this noble mission."