Protesters gathered outside Care International's headquarters

Many had been helped by Mrs Hassan or by Care International, the aid agency she worked for, BBC News 24 said.

Correspondent Claire Marshall said there was much support for Mrs Hassan amongst ordinary Iraqis, but that the rally was "completely unprecedented".

The Muslim Council in the city of Falluja - an insurgent stronghold - had also condemned the abduction, she said.

"Most people I speak to here are completely ashamed that somebody who's lived in the country for 30 years and worked on behalf of the Iraqi people, obviously so clearly and so strongly, should be the target of a kidnapping."

Protesters carried pictures of Mrs Hassan and banners calling for her captors to set her free.

"We demand the release of this woman who took part and exerted painstaking efforts in reconstructing Ibn al-Qif Hospital for spinal diseases," a wheelchair-bound protester told AP news agency.

Another, a teacher at an Iraqi school for the deaf, brought about 30 pupils to the demonstration because of Mrs Hassan's efforts on behalf of hearing-impaired Iraqis.

Prayers

On Sunday, Christian worshippers in Iraq prayed for the release of Mrs Hassan.

Parish priest al-Khori Rufaeel, deputy head of the Syrian Catholic Community, condemned her abduction, saying it did not serve the country's interests.

He also stressed during his sermon in Baghdad that Mrs Hassan had spent years working for Iraq and its people.

Reuters news agency reported that insurgent commanders in Falluja said they were not holding Mrs Hassan.

'Bad impression'

One of five guerrilla commanders, quoted by Reuters, said: "The resistance did not kidnap her because this would have left a bad impression of the resistance in the world."

Another said: "This woman works for a humanitarian organisation - she should not have been kidnapped."

Mrs Hassan has lived in Iraq for some 30 years.

They said there was no evidence that Jordanian militant Abu-Musab al-Zarqawi's Tawhid and Jihad group - which abducted and killed British hostage Kenneth Bigley - was involved.

In a video released on Friday, Mrs Hassan - who has dual Iraqi and British citizenship and is in her 60s - was seen in tears begging Tony Blair to withdraw troops to save her life.

Holy month

Her Iraqi husband Tahseen Ali Hassan also made a televised appeal for her release.

Addressing the captors, he said: "I beg you, in the name of Islam and Arabism, while we are in the holiest Islamic month, to return my wife.

"She considers Iraq her homeland. She loves Iraq and its people.

"This is why she devoted herself and her life to help her people in Iraq."

Mrs Hassan was abducted in Baghdad on Tuesday and is director of Care International's operations in Iraq.

She was seized from her car on the way to work by gunmen, one of whom was reported to have been wearing a police uniform.