In Haditha, 200km north-west of Baghdad, fighters with rocket-propelled grenades and mortars attacked a police station at dawn on Sunday.
After a 90-minute battle in which six policemen were wounded, the attackers took 21 captured policemen to the K-3 oil-pumping station area and shot them dead.
In nearby Haqlaniya, Brigadier Shahir al-Jughaifi, security chief in western Iraq, died in an attack on a police post.
Fighters killed another Iraqi police officer and wounded one in the town of Baquba, north-east of Baghdad, police said.
"A large number of attackers, estimated at about 200, ambushed the main police station in Haditha and another smaller one in Haqlaniya," an officer, speaking on condition of anonymity, said.
"The attackers disarmed the police, gathered them together and then shot them dead," he said.
Policemen found their colleagues with their hands tied behind their backs, while the attackers made off with their weapons and about 15 vehicles.
Seen as collaborating with the US-led military, Iraq's fledgling security forces are a top target for groups fighting to drive out foreign armies.
The attacks came a day after fighters launched coordinated attacks in Samarra, 140km east of Haditha, leaving 29 people dead and another 40 wounded.
Assailants stormed a police station, triggered at least two car bombs and fired mortars at government installations.
Falluja is now encircled by
US forces ready for an assault
One of the car bombs targeting the mayor's office used a stolen Iraqi police vehicle, the US military said.
Twenty-nine people including 17 police and 12 Iraqi civilians were killed throughout the city, the US military said.
The dead included the local Iraqi National Guard commander, Abd al-Razzaq Shakir al-Garmali, hospital officials said.
Forty other people including 17 policemen were injured, the US military said.
US warplanes and artillery pounded parts of Falluja on Sunday, but there was no sign American forces had begun an offensive to storm the stronghold of anti-US forces.
Residents said air strikes interspersed with artillery shelling had set off huge explosions in the city from about 3am (0000 GMT) onwards. There was no word on casualties.
Car bombs shattered the relative
calm of Samarra on Saturday
US marines relentlessly pounded the fighter enclave with artillery fire from Saturday night through Sunday morning, an AFP correspondent embedded with marines reported.
The bombardment of Falluja kept up pressure on Iraqi fighters and what the US military says are "foreign militants" led by Jordanian al-Qaida ally Abu Musab al-Zarqawi, based in the city. Falluja's residents deny such fighters are holed up there.
At least 12,000 troops, including four US military brigades and one Iraqi forces brigade, are ringing the city, a marine officer said.
They are awaiting a final go-ahead from interim Prime Minister Iyad Allawi.
Falluja has a population of about 300,000 but many families have fled to escape the expected US assault, part of the US-backed Iraqi interim government's drive to crush anti-US forces before elections scheduled for January.
The US military said it had launched seven air strikes on weapons caches in Falluja, 50km west of Baghdad, between dawn and midnight on Saturday.
In other incidents, a car bomber attacked a US military convoy on the main road to Baghdad airport, hitting a Humvee vehicle, witnesses said.
Aljazeera has learned that an unknown number of US soldiers were wounded in the incident on Sunday.
Other reports say that one US soldier died in the attack.
US troops sealed off the scene of the attack on the main road leading to the airport in south-western Baghdad.
On Saturday, a car bomber killed an Iraqi civilian and wounded three US soldiers on the same airport road.