Iraqi insurgents made their boldest attack yet on US forces in the northern city of Mosul, with an explosion in a packed dining tent at a military base, which killed at least 24 people, including 19 US soldiers.
The army said that the blast at Camp Merez at the airport south-west of the city also struck members of the Iraqi National Guard and civilian contractors.
President George Bush, sensing the public shock at the highest death toll from a single attack involving US soldiers in Iraq since the war ended, said: "We pray for them. We send our heartfelt condolences to the loved ones who suffered today. We just want them to know that the mission is a vital mission for peace," Bush said.
He added: "I'm confident democracy will prevail in Iraq. I know a free Iraq will lead to a more peaceful world."
The first reports blamed rocket or mortar fire for the explosion, but a military spokesman said last night that the source was "still unknown" and was being investigated.
The extremist Sunni group, Ansar al-Sunna, claimed responsibility and indicated in an internet statement that it might have been a suicide bombing. The group, responsible for beheading a number of hostages, has threatened to attack polling stations during next month's elections, which it has urged Iraqis to boycott.
Whether yesterday's was a planned attack or a chance hit, the US commanding officer in Mosul, Brig Gen Carter Ham, admitted that it had had "a very negative effect against multinational forces and our Iraqi partners."
Camp Merez is a sprawling military camp of temporary buildings, old Iraqi army barracks and tents to the south-east of the city centre, near the city's main airbase occupied currently by the US military.
Some 2,000 US personnel are stationed at the camp, along with 150 Iraqi soldiers, and a handful of US contractors.
The dining hall, a massive tent 100 metres long and 30 metres wide, is perched on a hill overlooking the base. It was built a year ago and is soft-skinned.
At midday when the mortars hit, the hall would have been packed with soldiers queueing for food inside a serving area, or seated at tables inside the dining area watching giant television screens.
Violence is increasing as the January 30th elections approach. On Sunday car bombers hit crowds, killing at least 61 people and wounding about 120.
The blast happened as a Washington Post/ABC News poll showed for the first time that the majority of Americans believe that it was not worth going to war in Iraq: 56 per cent said the costs outweighed the potential benefits, an eight-point rise on similar polls in the summer. - (Guardian Service); Additional reporting, Jack Fairweather