Car bombs have exploded at two police stations in the Baghdad area, killing at least eight people.
Iraqis fear Saddam Hussein's arrest will trigger further attacks
The deaths came in an attack in Husseiniya, north of the capital, while about four people were injured in a blast in the city's Amiriya district.
A second possible car bomb attack on the Amiriya station was foiled by police and the attacker arrested.
The incidents come a day after US officials announced the capture of former Iraqi leader Saddam Hussein.
A Toyota Land Cruiser packed with explosives was used to target the Zuhour police station in Husseiniya village, 30 km (18 miles) north of Baghdad.
Lieutenant Colonel Ali Amer said the vehicle drove through the razor fence
around the building and detonated next to the gate. Eight police officers died and 10 were injured, he told Associated Press.
Police officer Mohamed Hashim told Reuters that the attack on the Amiriya station, where the criminal investigation department is based, was a suicide operation.
"We were standing outside the police station when a very fast car came, we shouted to try and stop him but he detonated the car," he said.
Another potential attacker abandoned a vehicle packed with explosives after he came under fire from police officers and US troops.
Captain Brad Loudon said the man was arrested.
The BBC's Caroline Hawley, in Baghdad, said many Iraqis have said they feared an increase in such attacks following the arrest rather than an end to the violence.
On Sunday, 17 Iraqis were killed in an explosion outside police station in Khalidiyah, about 35 miles (60 km) west of Baghdad - the largest single attack on Iraqi police in the country.
Scores of Iraqis have been killed or injured in bomb attacks targeting police stations and those co-operating with coalition forces since the US-led invasion.
The US administrator, Paul Bremer, has called on Saddam Hussein's supporters to lay down their arms. But our correspondent says the resistance to the American occupation is much wider than Saddam Hussein's loyalists.