Ten of the bombings were in Baghdad, mainly in Shiite neighborhoods. Targets included a hospital, a restaurant and markets. At least 30 people were killed and more than 100 wounded, authorities said.

Officials in the Iraqi capital tightened security after the latest blasts, fearing that more devices could yet be detonated. There were long lines at vehicle checkpoints in the capital as the security services searched cars for explosives. Since the start of Ramadan on July 10, coordinated bombings and other attacks have intensified. That has revived fears that Iraq could be returning to the levels of sectarian violence seen in the last decade when the country moved to the brink of civil war following the American-led invasion in 2003.

In Kut, southeast of Baghdad, two car bombs exploded near a bus station, leaving six people dead and about 20 others injured, according to a medical source.

Two car bombs detonated in Basra, in southern Iraq, killing at least three people near a market and wounding 14 others, a police official said. And in Muthanna Province, a car bomb exploded at a market in the city of Smawa, killing six people and injuring 19, according to a police official.

There was also violence in Tikrit, north of Baghdad, where gunmen blew up a house belonging to an Iraqi Army officer, killing one person and injuring two.

While the violence is below levels seen during the peak of the insurgency in 2006 and 2007, bombings remain common and as many as 700 people are believed to have been killed this month.

There was no immediate claim of responsibility for the attacks on Monday, but in the past, coordinated bombings against Shiites have been orchestrated by Al Qaeda’s branch in Iraq.

Nine days ago Baghdad was hit by an explosion in the central Baghdad neighborhood of Karada. The police said it had killed nine people and wounded 17. That was part of a surge of violence that killed at least 46 people inside and outside of the capital.

Meanwhile, the commander of the Baghdad operations, Lt. Gen. Abdul Amir al-Shammari, said at a news conference that the security forces had recaptured 349 prisoners of around 800 who escaped from the Abu Ghraib prison this month.