The four men, from the UK, US and Canada who were kidnapped by a militant group in Iraq, are all associated with the North America-based ecumenical pacifist group Christian Peacemaker Teams (CPT).
The group, based in Chicago and Toronto, has long operated in the world's troubled regions in an effort to reduce violence.
The men are being held by a previously unknown Iraqi militant group
In the Middle East, it has been operating in Iraq intermittently for the past three years, and has had a presence in Gaza and the West Bank for the past decade.
CPT, which was founded in 1988, has previously operated in Afghanistan, Chechnya and Bosnia. It is still active in Colombia.
Full-time CPT members serve a three-year term and are supported by a larger reserve team who work for about eight weeks a year. A team consists of four to six people at any given time.
Members belong to various Christian denominations, but, while they say they are Christian, they emphasise that they are not missionaries.
The group describes its work as "truth telling", recounting the stories of ordinary individuals in areas of conflict.
Many of these stories are relayed to a wider audience in the members' home countries via e-mail, newsletters and public appearances. CPT is also active in lobbying government officials.
In Iraq, the group's work has focused on the issue of Iraqi detainees held by US forces. This has involved taking testimonies from families of detainees and former detainees alleging human rights abuses.
American Tom Fox who is being held in Iraq also worked in the West Bank with CPT
"We were the first to publicly denounce the torture of the Iraqi people held by occupation forces," CPT co-director Doug Pritchard told the BBC. He said this was months before the Western media reported on abuses at the notorious Abu Ghraib prison.
None of the CPT members have witnessed the alleged abuse at first hand or have been inside the military prisons.
In an interview with the BBC News website in December 2004, Peggy Gish, a CPT member, described how she spent 13 months on the ground listening to stories of Iraqi men and women who claim they had been wrongfully imprisoned, tortured and beaten by the occupying forces.
"We heard about very violent house raids in the middle of the night, in which US soldiers would storm in, and if the men did not get down immediately, they would knock them down and beat them," Ms Gish said.
The CPT (whose members often wear red hats) has been active in the West Bank for a decade
After collating the claims, CPT posted them on US and Canadian websites and urged people to lobby government officials.
CPT members also aim to find out what everyday life is like for ordinary Iraqis. Before his departure to Iraq, Briton Norman Kember - who is being held by a previously unknown militant group, The Swords of Truth - told a Christian radio station that he was hoping to meet ordinary Iraqis of various backgrounds and hear their stories.
According to Mr Pritchard, the team that has been kidnapped in Iraq had recently been meeting authorities responsible for electrical power plants and oil refineries, to find out what difficulties Iraqis face and the reasons for them.
He said they had also met other human rights organisations in the country.
Responding to a question about operating in dangerous situations such as war zones, Mr Pritchard said: "That's exactly where we work and it comes out of our own faith calling that soldiers take these risks every day and we respect the risks they take.
"We are convinced they are on the wrong track as soldiers, so we are challenging ourselves and asking: 'Do we not have as much faith and as much courage as soldiers have and are we willing to put our own lives on the line'?"
On its website, the organisation says volunteers are aware of the risks and that "CPT does not advocate the use of violent force to save lives of its workers" even if they are kidnapped or held hostage.
CPT has had a presence in the Middle East for the past decade. Its West Bank headquarters is in the town of Hebron.
Volunteers live among the Palestinians, accompanying children to school and ordinary people through Israeli checkpoints. They report what they perceive to be human rights abuses.
Operations include demonstrating against the Israeli separation barrier and standing in front of homes that Israeli forces have earmarked for destruction. Palestinian homes have been destroyed for a number of reasons, including punishment for suicide bombings, being built without permission from Israeli authorities and for what Israeli forces cite as security issues.