Margaret Hassan, who works for charity Care International, was taken hostage while on her way to work in Baghdad. Here are the main events since her kidnapping.
19 Oct: Mrs Hassan is seized by gunmen at 0730 Iraqi time. Hours later video footage of Mrs Hassan, with her hands bound behind her back and looking "very distressed", is shown on Arab TV station Al-Jazeera, which reports that an unnamed "armed Iraqi group" says it has kidnapped her.
20 Oct: Care International, which is headed by Mrs Hassan, says it has halted its operations in Iraq following the abduction. Her Iraqi husband Tahseen Ali Hassan makes an emotional appeal to the kidnappers to free her. Mr Blair and Irish prime minister Bertie Ahern stress every effort possible is being made to free her.
21 Oct: Mr Hassan makes a second appeal to the kidnappers to free his wife. Mrs Hassan's colleagues say they are hopeful she will be released and that an
enormous amount of work is being undertaken on the ground in Iraq to try and
secure her freedom.
22 Oct: Al-Jazeera TV shows a new video of Mrs Hassan weeping. She pleads with the British people to save her life and says she does not want to die like Ken Bigley.
22 Oct: Care International appeals on Arabic television for the release of Mrs Hassan.
23 Oct: Mrs Hassan's husband makes another televised appeal asking her captors to release her. "It was very painful to see my wife crying," he adds.
24 Oct: Christian worshippers in Iraq pray for Mrs Hassan's release. Reuters news agency reports that insurgent commanders in Falluja say they are not holding her.
25 Oct: About 200 people, many helped by Mrs Hassan or Care International, rally at the agency's Baghdad offices. They carry pictures of Mrs Hassan and banners calling for her captors to set her free.
27 Oct: Al-Jazeera TV broadcasts another video of Mrs Hassan looking confused and close to tears. She asks for British troops to be withdrawn, for Care International to close its office in Baghdad and for Iraqi women prisoners to be freed. It is still not known which group has kidnapped the aid worker.
28 Oct: Care International follows the wishes of Mrs Hassan's latest video plea by announcing it has closed down all its operations in Iraq. It once again calls for her release.
2 Nov: In Dublin Mrs Hassan's sister makes a plea for her release after meeting Mr Ahern, who reiterates his call for her freedom. Another video of Mrs Hassan surfaces, which al-Jazeera refuses to broadcast in full on humanitarian grounds. It is believed to show her making an emotional plea, then losing consciousness.
16 Nov: Mrs Hassan's family says it believes she is dead after being sent a video apparently showing her murder.
1 May 2005: Eleven people are arrested near Baghdad in a raid by Iraqi forces. Five men are said to have confessed to the killing of Mrs Hassan. Items belonging to her are reported to have been recovered.