The bomber who drove the car was also killed in the explosion.
Reuters reports four people dead, while another by AFP, reports the toll as standing at six.
Police officers said a small car driven by one man exploded 100 metres from the main police station in the town, west of Baghdad outside a boys secondary school.
A US military spokesman in Baghdad said she had no immediate information on the incident.
The latest incident comes after five explosions rocked central Baghdad on Monday, claiming the lives of 42 people and injuring 224 others.
Menwhile, five Iraqis have been arrested by US forces early on Tuesday in the city of Baquba, north-east of Baghdad. They are suspected of involvement in anti-US attacks.
Aljazeera’s correspondent reported that the arrests came as US forces launched search operations in the city.
Earlier on Tuesday morning, US forces came under attack in two separate incidents in the city of Samarra, north of Baghdad.
Witnesses told Aljazeera’s correspondent that a US military camp was targeted in the first attack. In the second incident, a US tank was damaged in an attack on a patrol in the al-Mafraq area, south of Samarra.
On Monday night, four American soldiers were wounded near the northern city of Mosul, Iraq's third-largest city. Two US patrols were ambushed.
One solider was wounded when insurgents attacked his convoy in southeastern Mosul and three others were injured, one seriously, when their patrol was attacked by rocket-propelled grenades and automatic weapons in the town of Tal Afar, just west of Mosul, the US command said.