Colonel Tareq al-Theybani of the Iraqi police said the bodies bore signs of torture, and were discovered on Sunday in an abandoned post office in the town of Juwayba, near Ramadi, capital of Anbar, a province west of Baghdad.
In recent months Sunni tribes from Anbar have united in a coalition to oppose al-Qaeda in Iraq, sending thousands of young men to join the government security forces and co-operating with US and Iraqi commanders.
The US military announced on Sunday that four soldiers were killed on Saturday when a roadside bomb ripped through a patrol in west Baghdad.
"Peace in Iraq will happen when citizens realise that they can express their ideas and views more effectively ... than with violence"
JBernar5, Toledo, USA
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Another soldier was killed the same day when a foot patrol was struck by a bomb in the south.
A sixth soldier was killed and five wounded, also on Saturday, in a bomb blast in Diyala province, where attacks are on the rise as fighters focus on areas beyond the reach of an intensive security operation under way in the capital.
A marine also died on Saturday during combat operations in Anbar, the military said without elaborating.
The deaths brought to 3,220 the US military's losses in Iraq since the March 20, 2003, invasion, according to an AFP count based on Pentagon figures.
Armed groups killed three people, including a policeman, in two separate incidents early on Sunday in Baghdad despite a massive security crackdown in the Iraqi capital.
Security officials said a policeman and a civilian were killed and five policemen wounded when a roadside bomb struck a police patrol near al-Mustansiriyah University in east Baghdad.
Another civilian was killed and one wounded in a mortar attack in central Baghdad's al-Fadhel district, a security official said.
Armed groups have managed to carry out attacks in Baghdad despite the presence of 90,000 US and Iraqi troops on the city's streets as part of Operation Fardh al-Qanoon.
In other news, Iraqi security forces have seized a cache of weapons, including a sniper rifle, and arrested seven suspects in a raid on the house of Dhafir al-Ani, a leading Sunni member of parliament.
|Medics treat one of the many casualties of|
Sunday's bomb attacks in Baghdad [AFP]
Brigadier-General Qassim Mussawi, an Iraqi military spokesman, said the troops found "65 Kalashnikov rifles and other weapons and seized four vehicles", which contained traces of explosives.
Ani is a former spokesman for Iraq's biggest Sunni faction, the Islamic Party, which forms part of the governing coalition.
It was not clear whether Ani was in his west Baghdad home on March 8, when the raid took place, and he was not reported among those detained.
'So far, so good'
As the fourth anniversary of the war approached with another violent day in Iraq, Robert Gates, the US defence secretary, said on Sunday it was too early to evaluate whether the latest US strategy was working but "so far, so good".
For his part, Stephen Hadley, the US national security adviser, said on Sunday that Democrats will assure failure in Iraq and waste the sacrifice of US soldiers with legislation in the House of Representatives to remove troops.
The House this week plans to vote on a war spending bill that includes a troop withdrawal deadline of September 1, 2008.
Hadley said: "If we do a premature withdrawal, then what we have is a situation where the Iraqi forces cannot handle the situation, which is the case now.