A suicide car bomb against a joint army-police patrol near Baghdad killed at least four people on Tuesday, the second such attack in the town of Taji in as many days, officials said.
Three soldiers were among the four killed in the blast that struck at around 11:00 am (0800 GMT) in Taji, 25 kilometres (15 miles) north of Baghdad, security and medical officials said.
Twelve others were wounded in the attack, they said.
The bomber targeted a military-police patrol near a prison in the town, the officials added.
The attack came a day after a suicide bomber blew himself up amid a group of anti-Qaeda militiamen collecting their salaries in Taji, killing 23 people and wounding dozens more.
On Sunday, another suicide car bomb followed by an assault carried out by grenade-throwing gunmen on a police headquarters in north Iraq killed 30 people.
No organisation has claimed responsibility for the deadly string of attacks, but Sunni militants including Al-Qaeda's front group often target security forces and government targets in a bid to destabilise the country and push it back to the sectarian war that blighted Iraq from 2005 to 2008.
The latest violence comes amid a political crisis pitting Prime Minister Nuri al-Maliki against his government partners as weeks of demonstrations have raged in Iraq's north and west calling for the premier's ouster.