The faultlines in Iraq are deepening as the country marks six years of occupation.
A suicide car bomb killed five US troops last week in the deadliest attack on foreign forces in Iraq for a year.
The occupying forces believed they would be able to draw down their troops and leave behind a relatively stable country.
But the latest deaths mark a dangerous turn for the occupation.
The attack in the northern city of Mosul came as large sections of the Awakening Councils, former resistance fighters who switched sides at the height of the insurgency, are turning their guns on the Iraqi government and US troops.
They are angry that promises to pay them a monthly wage and draw them into the new Iraqi army have been broken.
The US and its allies fear that these fighters are re-establishing connections with the resistance in Mosul, which was widely considered to be the last bastion of the insurgency.
In a sign of the shifting fortunes of Iraqi politics, sections of the Awakening Councils – who are largely drawn from among Sunni Muslims – joined supporters of Shia cleric Moqtada al-Sadr in a mass demonstration in Baghdad against the occupation last week.
The two forces had been deadly enemies until recently in the sectarian battles that raged in the country.
Now the Kurds, who largely supported the US invasion, have also taken to the streets of Mosul to demand the city be annexed into a potential independent Kurdish state in northern Iraq.
The growing dispute between Kurds and Arabs is in danger of turning northern Iraq into an ethnic time bomb.
A Nato airstrike killed six civilians and wounded 14 in an attack on a village in northeast Afghanistan on Monday this week.
The latest deaths come as Nato confirmed that it killed four civilians in a similar raid the week before.