But Sheik Qais al Khazali, the leader of Asaib Ahl al Haq (League of the Righteous) said the UK was to blame for the tragedy.
IT expert Peter Moore, was kidnapped in Iraq in 2007 and released two years later.
Glasgow-born Jason Cresswell, 39, latterly of Portlethen, near Aberdeen and Alan McMenemy, 34, of Milngavie, East Dunbartonshire, Alec MacLachlan, 30, from South Wales and Jason Swindlehurst, 38, of Lancashire were killed by their captors, who had originally been taken for hostage exchange. Sheik Qais al Khazali said Britain "was not serious" in negotiations and had regarded the bodyguards as "second-class citizens". He said was in prison when Mr Moore and his team were taken and said he was sorry for the deaths, adding the kidnaps and the killings should never have happened.
"I think that the British government is responsible for their deaths because it was not serious in the negotiations with the side that held them. If they were fast enough that wouldn't have happened. The British government concentrated only on Peter Moore. The bodyguards were second-class citizens. That was a surprise for us."
League of the Righteous is now a political force, as well as a military force, in Iraq.
The four security guards were abducted with Mr Moore as they escorted him to the Iraqi finance ministry.Around 50 to 100 militants in police uniforms ambushed the building, blindfolding the men and bundling them into a vehicle.
The group were moved every few months to different locations. A film shot by the kidnappers showed Mr McMenemy in a withdrawn state as he spoke of his psychological turmoil over his captivity.