Police captain Husam Mussayif said a man wearing a police uniform tried to drive into the police station compound and then detonated the vehicle when he was challenged.
"It was a suicide car bomb. A man claiming to be police showed up at the entrance and was allowed into the compound. Then he detonated," said a police source in Tikrit, 180km north of Baghdad.
"Eight cars are in flames and the building is severely damaged," he said, adding that the blast occurred at about 9.30am (0630 GMT).
Mussayif was wounded in the side and leg by shrapnel in the explosion.
"It was a suicide car bomb. A man claiming to be police showed up at the entrance and was allowed into the compound. Then he detonated"
Iraqi police source
The director of Tikrit hospital, Imad Juburi, said they had received 10 dead and 35 wounded, all police officers.
The bomber "detonated his vehicle in the middle of policemen who had gathered for the morning parade," Juburi said, citing the accounts of survivors.
Also on Thursday, a police chief in the northern Iraqi city of Kirkuk escaped an assassination attempt that killed three police officers.
Colonel Khattab Umar Arif, the apparent target of the attack said the bomb exploded as his convoy drove past, killing his guards and wounding others.
"Two vehicles in my escort were destroyed," he said, adding that the bomb exploded about 100 metres from his house, which he had just left.
Two policemen were killed in the
Kirkuk car bomb
Aljazeera learned three police officers died in the attack and seven were wounded.
Police sealed the area of the blast, close to a checkpoint leading to Kirkuk airport, where US forces in the city are based.
Two more Iraqi police officers were killed and seven people, including civilians, were wounded in a car bomb blast in the al-Iskandariya neighbourhood south of Baghdad, Aljazeera reported.
US soldiers killed
Two US soldiers were killed in separate attacks north of Baghdad on Thursday, the US military said.
One soldier was killed in a roadside bomb blast near the town of Qaryat, northeast of the capital, and another was killed in a blast near Samarra, 100km north of Baghdad.
Two soldiers were also wounded in the second explosion.
All of the soldiers were from Task Force Liberty, the unit charged with enforcing security in a large swathe of the country stretching from near the capital up to the Kurdish region.
The deaths raise to at least 1128 the number of US troops
killed in action in Iraq since the war began in March 2003.
Air strikes continue
Meanwhile, US forces used warplanes, including an AC-130, as they stepped up operations against fighters in the western al-Anbar province, the US military said on Thursday.
The operations on Wednesday were focused on the anti-US stronghold of Haqlaniya.
US marines have stepped up
operations in Haqlaniya
"US jets delivered two 500-pound bombs on insurgent fighting positions after insurgents ambushed a US marine patrol with small arms and heavy machine gun fire," a military statement said.
US forces also detained 29 fighters and seized several weapons caches in al-Anbar, the military said.
Marines were also continuing operations in Ramadi, the military said.