BAGHDAD (AP) — Insurgents assaulted a police headquarters in northern Iraq early Wednesday, killing nine policemen as part of a series of attacks that left at least 14 dead as the country grapples with a growing surge of violence.

The attack took place in the town of Bashmaya outside the city of Mosul, which has been one of the major flashpoints in a wave of bloodshed that has washed over the country since April and left more than 3,000 people dead. The scale of the violence is intensifying fears of a return to the widespread sectarian killing that pushed the country to the brink of civil war after the 2003 U.S.-led invasion.

A police official said nine policemen were killed and two wounded in the initial attack. An ambulance rushing to the scene was hit by a roadside bomb, wounding the driver and his assistant, the official said.

A medical official confirmed the casualty figures. Both officials spoke on condition of anonymity because they are not allowed to talk to the media.

Insurgents this year have regularly attacked security forces in Mosul, a longtime militant stronghold.

On Monday, a suicide bomber rammed his explosives-laden car into an army convoy, killing at least 13 people — including 10 soldiers. Police found the bodies of four off-duty policemen Tuesday on a road with bullet wounds in their heads. Gunmen in a speeding car also shot dead two other off-duty policemen as they were walking down a street.

Also Wednesday, a car bomb exploded as an army patrol passed by outside the northern city of Kirkuk, killing an officer and a solider, police Lt. Col. Abbas Qadir said. Five soldiers were wounded, he said. Kirkuk is 290 kilometers (180 miles) north of Baghdad.

And in Baghdad, police found three bullet-ridden corpses across the city, police and medical officials said on condition of anonymity as they were not authorized to brief media.

In the northern city of Tuz Khormato, about 200 kilometers (125 miles) north of Baghdad, a bomb hidden in a motorized cart exploded in a residential area, wounding 35 people and damaging several houses, police Col. Hussein Ali Rasheed said.

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The security situation in Iraq began to deteriorate after security forces cracked down in April on a protest camp in the northern city of Hawija, sparking clashes in which 44 civilians and one member of the security forces were killed, according to estimates by the United Nations.

Overall levels of violence have since escalated and insurgent attacks have become more audacious, including raids this week against two high-security prisons near Baghdad that killed dozens and set free hundreds of inmates, including al-Qaida-linked militants.

On Tuesday, al-Qaida's Iraqi branch claimed responsibility for the attack.