The International Committee of the Red Cross is temporarily ending its operations in much of Iraq amid concerns over the safety of its staff.
The ICRC has operated through three wars in Iraq
ICRC spokesman Florian Westphal said their Baghdad and Basra offices were closing given "the extremely dangerous and volatile situation" in the country.
A car bomb at the Red Cross headquarters in Baghdad last month killed 12 people.
It was the first suicide attack on the neutral Swiss-based ICRC in its 140-year history.
Refusing military protection
The ICRC spokesman refused to say how much the closures would affect the work of some 30 foreign staff and 600 Iraqis.
"The situation is so tense on the ground that we don't want to get into details," Mr Westphal was quoted as saying by the Associated Press.
He said the ICRC had received no direct threat but had taken its decision on the basis of an overall assessment of the situation.
"We are still discussing what to do with our foreign staff. The situation is extremely dangerous and volatile," he said
The blast on 27 October, which killed among others two ICRC guards, wrecked the Baghdad office. It prompted the organisation to reduce its foreign staff and forced the remaining employees into temporary accommodation.
The ICRC has faced a difficult choice about its role in Iraq where it has been operating for 23 years, through the Iran-Iraq war, the Gulf war in 1991 and the US-led invasion earlier this year.
"We must painfully
acknowledge that the ICRC as a large humanitarian
organisation has become a target of attacks for a group of
people," ICRC President Jakob Kellenberger said in an interview with a Swiss daily newspaper, the Tages-Anzeiger of Zurich.
The ICRC has been forced to reconsider how to carry out
its humanitarian work while protecting its employees, Mr Kellenberger said.
"In the coming weeks we will have to redefine our modus
operandi, the way we are deployed," he said.
For the organisation to do its work, it has to be accessible to the public but for its staff to be safe from attack, it would need military protection - something the ICRC has ruled out.
"This decision has to be seen in the context that we clearly decided against seeking any military protection for buildings or staff," Mr Westphal said.
Other aid agencies and non-governmental organisations have also been reviewing or reducing their operations. Many cut back or left after the UN headquarters in Baghdad was bombed in August, an attack which killed at least 20 people.
The ICRC has an essential role to play in Iraq.
One of its main functions, and for which it needs international staff, is monitoring the treatment of detainees, acting as an independent watchdog to make sure the coalition does not violate international humanitarian law.
Other tasks include supplying equipment and medicines to hospitals, helping hospitals with basic repairs and tracing missing people - all vital at a time of instability and conflict.
Mr Westphal stressed that the ICRC would remain present in northern Iraq.
"Our future activity will focus on visiting prisoners, re-establishing family contacts and providing emergency aid in the areas of water and medicine," he said.