A trio of attacks targeting Iraqi security forces have killed at least 18 people and wounded dozens more in locations near the capital Baghdad, officials have said.

The deadliest incident was near the southern town of al-Shumali where a car bomb exploded in front of a restaurant frequented by security officers, killing 13 people and wounding many more, officials and medics said.

Al-Shumali is just south of Hillah, located about 90km south of Baghdad. It is also a popular resting place for Shia Muslim pilgrims headed to the holy shrine of the Imam al-Hamza, located 4km south of the town.

Later on Wednesday morning, two soldiers were killed and 11 were wounded in a blast at a military camp near the town of Habbaniyah, 80km west of Baghdad, Iraqi officials said on condition of anonymity.

Explosives were detonated on a minibus that was carrying soldiers to a training area in western Iraq's Anbar province, they said.

"The soldiers finished their academic training and a bus took them to have breakfast at the restaurant in the base. When the bus reached the restaurant it exploded," an Iraqi army source told the Reuters news agency.

In the dawn attack, gunmen opened fire on a security patrol in a mixed Sunni-Shia neighbourhood in northeastern Baghdad, killing two policemen and wounding a third, according to a police official and a medic at Baghdad city hospital.

Al-Qaeda suspected

No group has claimed responsibility but Iraqi officials suspected al-Qaeda fighters had carried out the attacks

"Terrorist groups of al-Qaeda are standing behind this cowardly crime," Haider al-Zanbour, chairman of the security committee in Babel Council, said. "We have formed a team to investigate."

Assaults on Iraq's army and police have been rising as they prepare to take sole responsibility for security.

The US military is scheduled to fully withdraw its remaining 43,000 troops by the end of this year, although Iraqi politicians are trying to decide whether to ask to leave some troops beyond 2011 to continue to train their army and police.

Iraq became a battlefield for al-Qaeda after US invaded in 2003, although the group's numbers have shrunk since 2006-2007, after Sunni tribal chiefs joined forces with the US military.

On Monday, 22 Iraqi Shia pilgrims died in an ambush south of the town of Rutba, which lies along the main highway between Baghdad and Jordan. Officials blamed the attack on al-Qaeda.

According to figures from Iraq's interior and defence ministry, 45 police and 39 soldiers were killed in bombings and shootings in August.

The health ministry's statistics say 155 civilians were killed in the same time span.