British, American and Iraqi authorities are trying to secure the freedom of Margaret Hassan, the Irish-born aid worker kidnapped in Baghdad early yesterday.

British, American and Iraqi authorities are trying to secure the freedom of Margaret Hassan, the Irish-born aid worker kidnapped in Baghdad early yesterday.

A video broadcast on the Arabic television station al-Jazeera ­ which also showed her passport, credit cards and identity cards ­ was delivered by a militant group which claimed responsibility for the abduction, but did not identify itself or issue demands.

Tony Blair, the Prime Minister, said: "This is somebody who has lived in Iraq for 30 years, someone who is immensely respected, someone who is doing their level best to help the country. We don't know which group it is, so there's really a limit at this stage to what I can say to you. We will do whatever we can, obviously."

The authorities in Baghdad said they were deeply worried for Mrs Hassan's safety. Mrs Hassan, the director of Care International for Iraq for the past 12 years, was abducted by gunmen in west Baghdad as she drove to work just after 7.30am. The organisation does not employ armed guards. Her fellow workers said there were no warnings that she might be in danger, nor had she expressed any worries.

The kidnapping comes less than two weeks after the beheading of the British contractor Kenneth Bigley, who was held for three weeks by a group believed to be led by the Jordanian-born militant leader Abu Musab al-Zarqawi.

The abduction came as a shock even in Baghdad, a city which has become used to the routine of hostage taking. Mrs Hassan was a familiar and highly respected figure in Baghdad, where she lives with her Iraqi husband, and has dual Iraqi and British nationality.

A Care spokesman said last night: "As far as we know, Margaret is unharmed. She has been providing humanitarian relief to the people of Iraq in a professional career spanning more than 25 years.

"She considers herself an Iraqi national. Iraq is her home, and she never considered coming back to Britain."

The organisation, which employs 30 Iraqi nationals in its Baghdad office, today suspended operations in Iraq.

Several other women aid workers have been kidnapped in Iraq since the war, but all have been freed.

Simona Pari and Simona Torretta, both Italian, aged 29 and working for a humanitarian organisation in Baghdad, were released on 28 September. Nahoko Takato, a 34-year-old Japanese, was kidnapped and released along with several Japanese men.

Astrid van Genderen Stort, a spokeswoman for the UN High Commissioner for Refugees, said last night in Amman: "We, the UN, decided last year not to have international presence any more because we deemed the situation too dangerous. The kidnappings of the Italians should have alerted others to the dangers of working in Iraq."

A sustained mortar attack on the headquarters of the Iraqi National Guard yesterday morning at Mushahidah, 25 miles north of Baghdad, killed four people and injured more than 80. Another mortar attack, in central Baghdad, killed an American contractor and injured a US soldier.

US warplanes and helicopter gunships carried out another night of air strikes on the rebel stronghold of Fallujah. There were also exchanges during the day with three Humvees set alight in the American ranks by a car bomb.

US Marines clashed with militants in the nearby city of Ramadi where some of the foreign fighters who escaped the US encirclement of Fallujah have supposedly taken refuge.

South of Baghdad, US forces arrested nearly 130 suspects in an area near where British forces being sent from Basra are likely to be deployed.

THE CHARITY VOID

Care International, which today suspended operations in Iraq, has been active in Iraq since the 1991 Gulf War. It pulled out its international staff last autumn and directed its Iraqi relief work from the Jordanian capital, Amman.

The only international non-governmental organisation to have maintained programmes in central and southern Iraq, Care employs 30 Iraqi nationals in its Baghdad office. Other aid agencies, including Médecins sans Frontières, have also pulled out international staff and relocated to Jordan. The United Nations, whose Iraqi headquarters was attacked in August last year, no longer has international staff in Iraq.

The International Red Cross, which reduced foreign staff to 29 after the bombing of its headquarters in October last year, operates with about 429 Iraqi staff. The European Union relies on Care and the International Red Cross to direct its aid to Iraqis.