BAGHDAD  — A string of nearly a dozen apparently coordinated bombs and a shooting in cities across Iraq killed at least 32 and wounded dozens Sunday, extending a wave of violence that is raising fears of a return to widespread killing a decade after the U.S.-led invasion.

Violence has spiked sharply in Iraq in recent months, with the death toll rising to levels not seen since 2008. Nearly 2,000 have been killed since the start of April.

Most of the car bombs hit Shiite-majority areas and were the cause of most of the casualties, killing 26. The blasts hit half a dozen cities and towns in the south and center of the country. There was no claim of responsibility for any of the attacks, but they bore the hallmark of al-Qaida in Iraq, which uses car bombs, suicide bombers and coordinated attacks to target security forces, members of Iraq's Shiite majority, and others.

The blasts began when a parked car bomb went off early morning in the industrial area of the city of Kut, killing three people and wounding 14 others. That was followed by another car bomb outside the city targeted a gathering of construction workers that killed two and wounded 12, according to police.

In the oil-rich city of Basra by the Gulf coast in southern Iraq, a car bomb exploded in a busy downtown street, police said. As police and rescuers rushed to the scene of the initial blast, the second car exploded. A total of six people were reported killed. Cleaners were seen brushing off debris of the car bomb that damaged nearby cars and shops.

About an hour later, two parked car bombs ripped through two neighborhoods in the southern city of Nasiriyah, killing one and wounding 17, another police officer said.

And in the town of Mahmoudiya, two civilians were killed and nine wounded when a car bomb went off in an open market.

In the Shiite holy city of Najaf, a blast struck a produce market, killing eight and wounding 28. Afterward, watermelons, tomatoes and apples were scattered on the ground where a bulldozer was loading charred and twisted stalls and cars into a lorry.

And in Madain, a roadside bomb and then a car bomb exploded, killing three and wounding 14, while in Hillah, a car bomb exploded in a parking lot, killing one and wounding nine.

The shooting happened near the restive northern city of Mosul. Police officials say gunmen attacked police guarding a remote stretch of an oil pipeline, killing four and wounding five. Mosul has been the scene of some of the deadliest unrest outside of the Baghdad area in recent weeks.

In the northern city of Tuz Khormato, a roadside bomb targeted a passing police patrol, killing two policemen and wounding another, another police officer said.

Medical officials confirmed the casualty figures. Officials spoke on condition of anonymity as they weren't allowed to release the information.

The attacks came a day after the leader of al-Qaida's Iraq arm, known as the Islamic State of Iraq, defiantly rejected an order from the terror network's central command to stop claiming control over the organization's Syria affiliate, according to a message purportedly from him. Abu Bakr al-Baghdadi's comments reveal his group's determination to link its own fight against the Shiite-led government in Baghdad with the cause of rebels trying to topple the Iran-backed Syrian regime.