Suspected Sunni Muslim militants killed four state-backed Sunni fighters in Iraq on Saturday, security sources said, apparently viewing them as collaborators with the Shi'ite-led government of a nation plagued by sectarian hatred.
Sunni-Shi'ite tensions in Iraq have been amplified by the conflict between mostly Sunni rebels and President Bashar al-Assad's Alawite-dominated forces in neighbouring Syria.
The four "Sahwa" militia fighters were killed in an attack on their headquarters on the outskirts of Garma, 9 km (six miles) east of Falluja, a city in the western province of Anbar.
Gunmen also ambushed and kidnapped 10 Sunni policemen near Ramadi, the capital of Anbar, a Sunni heartland bordering Syria.
There was no immediate claim of responsibility for the attacks, but Sunni militant groups have been behind previous violence targeting security forces in a campaign to destabilise the Baghdad government, which they reject as illegitimate.
When Sunni-Shi'ite bloodshed was at its height in 2006-07, Anbar was in the grip of al Qaeda's local affiliate, the Islamic State of Iraq, which has regained strength in recent months.
Sahwa or "Awakening" fighters are Sunni tribesmen who helped U.S. troops subdue al Qaeda in 2006. They are now on the government payroll and are often targeted by Sunni militants.
In other violence, tribesmen clashed with security forces and set four of their vehicles ablaze after a woman and three of her young children were killed in an army raid north of Ramadi.
Minority Sunnis, embittered by Shi'ite dominance since the overthrow of Saddam Hussein by U.S.-led forces in 2003, have been staging street protests against Shi'ite Prime Minister Nuri al-Maliki since December. A bloody government raid on a Sunni protest camp in Hawija last month ignited a surge of violence.
Monthly death tolls are well below those of 2006-07, when they sometimes topped 3,000, but more than 700 were killed in April by a U.N. count, the highest figure in almost five years.
At least 72 people died in attacks on Friday, 43 of them in two bombings outside a Sunni mosque in the city of Baquba.