-Reuters -

More than 60 people were killed in a series of car bomb explosions targeting Shias across Iraq on Monday, police and medics said, part of the worst sectarian violence since US troops pulled out in December 2011.

No group claimed responsibility for the bombings. Iraq is home to a number of insurgent groups, including the al Qaeda-affiliated Islamic State of Iraq, which has previously targeted Shias in a bid to provoke a wider sectarian confrontation.

Prime Minister Nuri al-Maliki said Monday he will overhaul Iraq's security strategy as a two-day wave of violence killed 72 people including 24 police, bringing the month's death toll from unrest to 349.

"We are about to make changes in the high and middle positions of those responsible for security, and the security strategy," Maliki said at a news conference in Baghdad.

"We will discuss this matter in the cabinet session tomorrow (Tuesday) to take decisions," Maliki said, without providing further details. "I assure the Iraqi people that they (militants) will not be able to return us to the sectarian conflict" that killed tens of thousands of people in Iraq in past years, he added.

Nine people were killed in one of two car bomb explosions in Basra, a predominantly Shia city 420 km southeast of Baghdad, police and medics said.

"I was on duty when a powerful blast shook the ground," said a police officer near the site of that attack in the Hayaniya neighborhood. "The blast hit a group of day laborers gathering near a sandwich kiosk," he added, describing corpses littering the ground. "One of the dead bodies was still grabbing a blood-soaked sandwich in his hand." Five other people were killed in a second blast inside a bus terminal in Saad Square, also in Basra, police and medics said. In Baghdad, at least 30 people were killed in car bomb explosions in Kamaliya, Ilaam, Diyala Bridge, al-Shurta, Shula, Zaafaraniya and Sadr City - all areas with a high concentration of Shias.

A parked car bomb also exploded in the mainly Shia district of Shaab in northern Baghdad, killing 12 people and wounding 26 others, police and hospital sources said. In a separate incident, police said a parked car blew up near a bus carrying Shia Muslim pilgrims from Iran near Balad, 80 km (50 miles) north of Baghdad, killing five Iranian pilgrims and two Iraqis who were traveling to the Shia holy city of Samarra.

In the western province of Anbar, the bodies of 14 people kidnapped on Saturday, including six policemen, were found dumped in the desert with bullet wounds to the head and chest, police and security sources said.

When Sunni-Shia bloodshed was at its height in 2006-07, Anbar was in the grip of al Qaeda's Iraqi wing, which has regained strength in recent months.

In 2007, Anbar's Sunni tribes banded together with US troops and helped subdue al Qaeda. Known as the "Sahwa" or Awakening militia, they are now on the government payroll and are often targeted by Sunni militants as punishment for co-operating with the Shia-led government.

Three Sahwa members were killed in a car bomb explosion as they collected their salaries in the city of Samarra, north of Baghdad, police said.

Iraq's delicate intercommunal fabric is under increasing strain from the conflict in neighbouring Syria, which has drawn Sunni and Shia Muslims from across the region into a proxy war. Syrian President Bashar al-Assad's main regional ally is Shia Iran, while the rebels fighting to overthrow him are supported by Sunni Gulf powers Saudi Arabia and Qatar. Iraq says it takes no sides in the conflict, but leaders in Tehran and Baghdad fear Assad's demise would make way for a hostile Sunni Islamist government in Syria, weakening Shia influence in the Middle East.

The prospect of a shift in the sectarian balance of power has emboldened Iraq's Sunni minority, embittered by Shia dominance since the overthrow of Saddam Hussein by US-led forces in 2003.