Iraq's once most violent province of Anbar and its flashpoint city of Fallujah have been relatively calm for more than three years after Sunni tribes and anti-U.S. insurgent groups turned to cooperate with the U.S. troops and Iraqi security forces against al-Qaida network in Iraq.

In northern Iraq, nine soldiers were killed when gunmen blew up a bomb and opened fire on three vehicles carrying soldiers of the Iraqi 3rd Division, on a main road outside Mosul, the capital city of Nineveh province, an anonymous provincial police source told Xinhua.

Five soldiers and a civilian were also wounded by the attack, the source said.

The soldiers were leaving their military bases for vacation and were heading to their homes on a highway near the city of Mosul, some 400 km north of Baghdad, when the insurgents ambushed their vehicles, the source added.

Nineveh province has been a stronghold of insurgent groups and al-Qaida fighters despite major security crackdowns by the U.S. troops and Iraqi security forces to uproot the insurgency which erupted shortly after the U.S.-led invasion in 2003. Violence is still common in Iraqi cities as security deteriorated, causing a setback to the efforts of the Iraqi government to restore normalcy in the country about two weeks after the U.S. military announced withdrawal of its combat troops from the war-torn country.