Three Iraqi policemen were killed on Saturday afternoon south of Baghdad, an Interior Ministry spokesman said.
He said the three died when their police car blew up in raids against armed fighters in the Latifiya area, just south of the capital.
"We know that a police vehicle was attacked and blown up but we do not have the details now. Three were dead and several wounded but we don't have the exact amount," said the spokesman.
The attack came hours after a bomber detonated his vehicle near a police academy in the northern town of Kirkuk.
At least 22 people were killed and 20 wounded in the attack.
Police said the head of the bomber was found among the debris scattered by the blast about 150 metres from the police building. One police car and four civilian vehicles were destroyed.
In a separate incident, at least 12 people were killed and 60 others wounded as clashes erupted in the northern town of Tal Afar, Iraqi journalist Ammar al-Zubaidi told Aljazeera on Saturday.
The fighting in Tal Afar, near the city of Mosul, began after US troops and Iraqi forces encircled al-Sarai and Hasankul districts in the town, al-Zubaidi said.
Also, a US military helicopter was forced to land near Tal Afar on Saturday. Two crew members aboard the UH-58 were injured, a US military spokesman said.
He said it was not immediately clear what forced the helicopter to land but it happened as fighting raged in the area.
Located near Mosul in the north,
Tal Afar has seen fierce clashes
Explosions and machine-gun fire have continued to rock Tal Afar, about 390km north of Baghdad, witnesses say.
Elsewhere in Iraq, a US military Humvee was destroyed on Saturday morning in the district of al-Hashimiya, west of the central city of Baquba, Aljazeera has learnt.
The US vehicle was about to detonate a landmine when an explosive device planted on the main road blew up, wounding a number of US soldiers, sources told Aljazeera.
A spokesman at the Tal Afar hospital said "the number of casualties is expected to rise as the clashes and bombing by helicopters are continuing".
"Many houses have been bombed and destroyed with the residents still inside," Dr Khalil Ibrahim Rashid said.
"All casualties are civilians, including women and children."
Dr Rashid added the town had been sealed off since early Saturday morning, "turning it into a banned military zone".
Tal Afar has witnessed much bloodshed in recent weeks. About 30 civilians were wounded in apparent crossfire during clashes between US forces and suspected resistance fighters on 29 August.
Attacks on oil infrastructure have
repeatedly interrupted exports
Against this backdrop of fierce clashes, oil pipelines in both the north and south of Iraq were attacked on Saturday.
A pipeline near the main southern Iraqi city of Basra was attacked, less than two days after northern exports were halted by a huge attack on a pipeline to Turkey police said.
Firefighters struggled on Saturday to put out the blaze caused by the explosion near Hartha, 30km north of Basra, police Colonel Nuri Muhammad said.
A South Oil Company official said on condition of anonymity that technicians were forced to close the pipeline, which carries 15,000 barrels of crude a day from the Nahran Omar oilfields to an export storage tank called Zubayr-1 in the Faw peninsula.
In northern Iraq, a refined oil products pipeline has also been attacked, a security official said.
A bomb exploded underneath the pipeline, which runs from the oil centre of Kirkuk to Iraq's biggest refinery at Baiji, according to Ahmad al-Ubaidi of the North Oil Company. Resistance fighters have launched repeated attacks on Iraq's vital oil industry in a bid to undermine the interim government.