(Reuters) -

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

The attacks brought the number killed in sectarian clashes in the past week to over 200, and tensions between Shi'ites, who now lead Iraq, and minority Sunni Muslims have reached a point where some fear a return to all-out civil conflict.

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

Nine people were killed in one of two car bomb explosions in Basra, a predominantly Shi'ite city 420 km (260 miles) 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 Shi'ites.

A parked car bomb also exploded in the mainly Shi'ite 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 Shi'ite 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 Shi'ite holy city of Samarra.

CORPSES FOUND

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-Shi'ite 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 U.S. 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 Shi'ite-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 neighboring Syria, which has drawn Sunni and Shi'ite Muslims from across the region into a proxy war.

Syrian President Bashar al-Assad's main regional ally is Shi'ite 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 Shi'ite influence in the Middle East.

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

Thousands of Sunnis began staging street protests last December against Shi'ite Prime Minister Nuri al-Maliki, whom they accuse of marginalizing their sect.

A raid by the Iraqi army on a protest camp in the town of Hawija last month ignited a bout of violence that left more than 700 people dead in April, according to a U.N. count, the highest monthly toll in almost five years.

At the height of sectarian violence in 2006-07, the monthly death toll sometimes topped 3,000.

(Additional reporting by Aref Mohammed in Basra, Kamal Naama in Ramadi, Ghazwan Hassan in Tikrit and Ahmed Rasheed in Baghdad; Writing by Isabel Coles; Editing by Mike Collett-White and Angus MacSwan)

By Kareem Raheem