Special report: Tension escalates in Iraq 　

    FALLUJAH, Iraq, July 13 (Xinhua) -- Two explosive charges blew up coordinately outside a house of a police officer in the city of Fallujah on Sunday, killing four policemen and wounding eight others, a local police source said.

    A roadside bomb went off in front of the house of a police officer in central Fallujah in the morning while a convoy of police vehicles arrived to take the officer to his office in the city, the source told Xinhua on condition of anonymity.

    Another roadside bomb detonated while people and police forces gathered to evacuate the casualties, wounding four policemen and four civilians, the source said.

    Anbar province, which includes Fallujah some 50 km west of Baghdad, was a stronghold of Sunni insurgents since the U.S.-led invasion in 2003. The city now is relatively calm after violence dropped sharply since late 2006.