Margaret Hassan, a kidnapped aid worker in Iraq, was believed murdered after Al Jazeera television said last night it had received a video showing a hooded militant shooting a blindfolded woman in the head.

Hassan, Irish-born and with dual British and Iraqi nationality, was seized by gunmen on her way to work in western Baghdad early in the morning.

She headed CARE International's operations in Iraq and had lived with her husband in the country for 30 years.

Hassan's family in London said they believed she was the victim in the video, and British Foreign Secretary Jack Straw said analysis of the video showed Hassan has "probably been murdered".

Hassan's husband, Tahseen Ali Hassan, said he had heard of the video but did not know whether it was authentic.