The United Nations may not have been granted a key role in the reconstruction of post-war Iraq, but it continues to carry out a variety of functions in the country.
Several agencies operate out of Baghdad, including the World Food Programme (WFP), the United Nations Children Fund (Unicef), and the United Nations Development Programme (UNDP).
WFP continues to help distribute food in Iraq
Many of them carry out the same tasks now as they did before the US-led invasion of the country - a war which was not fought with the support of the UN.
The UN returned to re-establish a permanent presence in Iraq in May, after official hostilities had ended, setting up its headquarters at the Canal Hotel.
Sergio Vieira de Mello was appointed as the UN's special representative to the country.
The mandate was limited to assisting and advising, but not controlling in any way, the development of new legal and political institutions in Iraq.
The extent of his involvement - even in an advisory role - in coalition decision-making is unclear.
There was no obvious participation on his part in the formation of the new governing council for Iraq, which was billed as one of the key steps in the country's move away from an autocratic regime to a democracy.
The WFP meanwhile, which played a key role in helping to keep people fed under Saddam Hussein, continues to play an important role in food distribution in post-war Iraq.
It is currently involved in supporting the Iraqi Ministry of Trade distribute 27 million food rations each month.
It has already been shaken by the insecurity which has plagued Iraq since the war ended, and in July announced that it was pulling its staff out of a major Baghdad warehouse after it was attacked by several hundred looters.
The UNDP has, for its part, been using its own engineers and local contractors to help rebuild the country's infrastructure.
It recently completed the rehabilitation of two sewage pumping-stations serving about 270,000 inhabitants in Basra, in southern Iraq.
History of HQ
The Canal Hotel, the headquarters of the UN in Baghdad and the target of Tuesday's attack, was once a hospitality training centre.
The three-storey building in a sparsely-built area of the capital was given to the UN in the early 1990s after the first Gulf War.
UN weapons inspectors from the now defunct Unscom set up their offices on the top floor of the hotel and carried out their work from there until 1998, when they left Baghdad.
Weapons inspectors returned to the hotel in November 2002 under a fresh UN mandate to search the country, and stayed there until March, 2003.
All foreign UN employees were evacuated that month, just before the war started.