Kidnappings are a constant danger for foreign nationals working in Iraq. As yesterday's events show, it is not just soldiers who are at risk.

British contractors and security guards have flocked to Iraq in recent years, lured by high wages and tax-free earnings.

Three British civilians have been snatched since troops entered Iraq in 2003. Norman Kember, 76, was rescued by British forces but Ken Bigley, 62, and Margaret Hassan, 59, were both murdered.

Mr Kember was in the country as part of a Christian Peacemaker Team when he and three colleagues - American Tom Fox and Canadians James Loney and Harmeet Singh Sooden - were taken on November 26, 2005.

Mr Fox was killed but the other captives were rescued on March 23 last year, after a frantic campaign to secure their release.

When British Special Forces raided the building where the hostages were being held, the captors fled. In November, Iraqi forces arrested several suspects but Mr Kember refused to testify against them. On his release, Mr Kember said: "I do not believe that a lasting peace is achieved by armed force, but I pay tribute to their courage and thank those who played a part in my rescue."

Mrs Hassan and Mr Bigley were killed before they could be rescued.

Mr Bigley was a civil engineer from Liverpool who worked for reconstruction company Gulf Supplies and Commercial Services.

He was taken, along with Americans Jack Hensley and Eugene Armstrong, in the al-Mansour district of Baghdad on September 16, 2004. Mr Bigley was beheaded on October 7 and a video of his murder was posted online.

Other videos had previously been released of Mr Bigley pleading with the British government to meet the demands of his captors.

Mrs Hassan had lived in Iraq since 1972 and even learnt Arabic and became an Iraqi citizen under Saddam Hussein's regime.

When she was kidnapped, she was head of Iraqi operations for international relief agency CARE. Her kidnappers made no specific requests but a film of her asking Tony Blair to remove British troops from Iraq was released. Four weeks after her capture, she was killed.

Although British security guards have been killed and injured in Iraq, this is believed to be the first time any have been kidnapped. However, Italian security guard Fabrizio Quattrocchiwas taken and killed while working for a US-based firm.

His colleagues Umberto Cupertino, Maurizio Agliana and Salvatore Stefio were also taken but were later released unharmed.

Yesterday Mr Kember said the latest abductions would result in a period of "extreme worry" for families of the kidnap victims. He added: "I don't even know if they have been told yet. But it is they that suffer."

Paul Bigley, brother of Ken Bigley, said he hoped they would be released swiftly.

He said: "I have no idea who they are, or what nationality, but I would gladly speak to their families if they want to speak to me. I would like to tell them to stay strong and hang in there."