"A patrol from 1st Battalion, 23rd Infantry Regiment was engaged by 12 assailants in a truck with a rocket-propelled grenade near Al Thubat," a US statement said. "The patrol returned fire with a missile, destroying the truck and killing all 12 assailants."
A dusk-to-dawn curfew was imposed in the city of Mosul, 390 kilometres north of Baghdad, after the clashes.
While, a US marine has been killed and another wounded in the Iraqi insurgent bastion of Fallujah since the midday (0800 GMT) Saturday start of a unilateral cease-fire by the US-led coalition, the US Marine Corps said.
"Since the suspension was called, the marines have sustained one marine killed and one wounded in Fallujah," a statement said, confirming that they had been respecting the unilateral ceasefire ordered by coalition commanders.
The marines said the pause was intended to "allow meetings between members of the interim Governing Council and Fallujah leadership for delivery of additional humanitarian supplies and to allow residents of Fallujah to tend to wounded and dead."
But they charged that their insurgent foes had failed to respect their humanitarian gesture, instead targeting relief convoys, which had been allowed to enter the town.
A member of the paramilitary forces in Iraq was killed and another wounded when gunmen opened fire on their checkpoint near city of Kirkuk, a security source said.
"The attack took place at 9:30 (0530 GMT) on Saturday. It was carried out by armed men who used rocket-propelled grenades," Anwar Hamad Amin, an officer in the Iraqi Civil Defence Corps, told AFP.
Two ICDC vehicles were damaged in the attack in Jabal Hemrin, south of Kirkuk.
Meanwhile, a convoy of US army oil tankers came under rocket-propelled grenade attack in Baghdad's western suburb of Abu Ghraib, a witness told AFP.
"Several tankers are on fire," Ammar Salim told an AFP correspondent who could not approach the scene because US troops had immediately cordoned off the area. Smoke rose above the area.
A US army spokesman could not confirm the attack.
Salim said the insurgents were apparently trying to "disrupt supply lines for the US army."
Most of the recent fighting in Iraq has been between foreign troops and either Shia militants in southern and central Iraq or Sunni insurgents in Baghdad and the west.
But there have been demonstrations in support of those fighting the occupation in many towns to the north, several of which have turned violent.