Seven people were killed and at least 15 wounded on Wednesday when a man detonated explosives packed in his car in central Iraqi city of Ramadi, police said.
"A suicide bomber blew up his car," police spokesman for al-Anbar Province Rahim Zubn told Baghdad's Aswat al-Iraq news agency.
The bomber and two policemen were among those killed when the car bomb exploded as a police patrol passed the Great Mosque of Ramadi, about 110 km west of Baghdad, Zubn said.
Police said they imposed a curfew in several neighbourhoods of the city, capital of al-Anbar province, following the attack.
Wednesday's bombing was followed by a day of mass demonstrations in nearby Falluja, a former insurgent stronghold, following the arrest of the city's former police chief and his deputy on charges of working with Al Qaeda.
More than 200 people gathered in the city to demand that the interior ministry release the city's former police chief, Colonel Faisal Ismail, and his deputy, Eissa al-Sari.
Police in Falluja told DPA they arrested the two on charges of working with Al Qaeda over the past three years and of involvement in several murders and illegal detentions during the same period.
They added that they had also arrested three men on suspicion of torturing and murdering an 11-year-old boy in al-Saqlawiya, some 12 km north of Falluja, because his father was a police officer.
Once in detention, the men confessed to the crime and other crimes committed in the city, police said.
Falluja, some 60 km west of Baghdad, is in the middle of Iraq's Sunni Muslim heartland. Following the US-led invasion of the country in 2003, it was the site of some of the worst fighting between US forces and Sunni insurgents.
Local Sahwa (Awakening) militias allied with the government had largely pacified the city by last year, though recent attacks have sparked fears the calm may be cracking.
In one such attack June 25, three Iraqi policemen were killed by a roadside bomb as they patrolled an area east of the city. A fourth died when gunmen sprayed a checkpoint with automatic fire.