(Updates Ramadi fighting, adds bombs in north)
BAGHDAD, Jan 19 (Reuters) - Iraqi Sunni Muslim tribesmen backed by police special forces and helicopter gunships attacked al Qaeda-linked militants in the city of Ramadi on Sunday, but halted the assault after at least eight of their number were killed, police and health officials said.
Police and local officials said the ground forces had retaken a police station in al-Hamthiya on the eastern outskirts of the city after helicopters fired missiles and machineguns at militants, but made no major advances.
The fighting in Ramadi, capital of the Sunni province of Anbar, was the heaviest in several days. A health official said at least eight police and tribal fighters had been killed.
"Our ambulance crew failed to retrieve more bodies left in dangerous areas," said the official, who asked not to be named.
There was no word on casualties among the militants.
The Islamic State in Iraq and the Levant, an al Qaeda offshoot also fighting in Syria, and its local allies overran parts of Ramadi, as well as the nearby city of Falluja, on Jan. 1 after security forces broke up a Sunni protest camp near Ramadi and arrested an outspoken Sunni lawmaker.
State security forces and Sunni tribesmen opposed to al Qaeda regained control of most of Ramadi earlier this month, but militants retain footholds on the edges of the city.
The authorities imposed an indefinite curfew in Ramadi, 100 km (60 miles) west of Baghdad, on Sunday to try to avert civilian casualties during the fighting, police said.
Army units have also deployed around Falluja, but Prime Minister Nuri al-Maliki has ruled out an all-out assault for now, saying the city's tribes must evict al Qaeda militants themselves.
Earlier in the day, gunmen wearing army uniforms killed at least six government-backed Sunni militiamen at a checkpoint near Baquba, 65 km (40 miles) northeast of Baghdad, police said.
They said the victims included the local leader of the "Sahwa" (Awakening) tribal militia, along with two of his sons.
Sahwa fighters, who helped U.S. troops turn the tide against al Qaeda-linked militants in Iraq from 2006 onwards, are often targeted by insurgents battling the Shi'ite-led government.
Two years after U.S. troops left Iraq, violence has climbed back to its highest levels since the Sunni-Shi'ite bloodletting of 2006-2007, when tens of thousands of people were killed.
The United Nations says nearly 9,000 people died violently in Iraq last year, all but 1,050 of them civilians.
North of Baghdad, a car bomb and a roadside bomb exploded in Tuz Khurmatu, a town contested between Arabs and Kurds, on Sunday, killing two people and wounding 10, police said.
In Kirkuk, a northern city at the heart of the Arab-Kurdish dispute, a car bomb killed a passer-by and wounded eight.
The toll from violence on Saturday rose to at least 32 killed, including six men involved in an attack on a juvenile prison in Baghdad, and 75 wounded, police and medics said. (Reporting by Ahmed Rasheed in Baghdad, Mustaf Mahmoud in Kirkuk and Ghazwan Hassan in Tikrit; Writing by Alistair Lyon; Editing by Kevin Liffey)