There was no immediate claim of responsibility for the attacks, which also wounded more than 200 people. But authorities have feared al-Qaida or its Sunni sympathizers would try to thwart next week's annual Arab League summit.
The gathering is to be held in Iraq for the first time in a generation. Plans for Baghdad to host the meeting last year were postponed, in part because of concerns about Iraq's security.
One of the deadliest strikes Tuesday hit the Shiite holy city of Karbala, where officials said two car bombs exploded in a crowded shopping and restaurant area. Thirteen people were killed and another 50 were wounded in that attack, said local provincial council member Hussein Shadhan al-Aboudi.
"The intention of these attacks is to destabilize the security situation in Karbala and other Iraqi cities and to shake the people's confidence on the government," al-Aboudi said. "It seems that the terrorists want to abort the upcoming Arab Summit in Baghdad. The message is directed to the Arab leaders that Iraq is not safe enough to be visited."
Karbala, 50 miles (80 kilometers) south of Baghdad, is a destination for thousands of Shiite pilgrims from around the world who visit the golden shrines of two revered imams each day. Five Iranian pilgrims were among the dead.
The wave of violence began after dawn Tuesday.
Militants blew up the house of a police official in the western city of Fallujah, planted bombs near the fortified Green Zone and shot up a security checkpoint in Baghdad, set off an explosion at a police station in the northern city of Kirkuk and attacked restaurants and shopping areas in two southern towns.
In all, eight cities were hit in attacks that mostly appeared to target police and government officials.
Police and health officials in each city who confirmed the casualties spoke on condition of anonymity because they were not authorized to speak to the media.
Saman Majid, a cameraman for the Kirkuk police department said he had just arrived at work when the bomb outside the station exploded. He said he was wounded by small shrapnel that hit his head and ran to the Kirkuk General Hospital for treatment instead of waiting for an ambulance.
"I quickly got out of my car to see burned bodies trapped inside the cars," he said. "Dozens of cars were on fire. It was a scene from hell, where there is only a huge fire and dead people and nothing else."
Thirteen people, most of them policemen, were killed in Kirkuk, said Brig. Gen. Sarhad Qadir. An additional 59 were wounded. Kirkuk is 180 miles (290 kilometers) north of Baghdad.
Officials have been bracing for attacks in the run-up to the Arab League summit during which the Shiite-led government hopes to showcase Iraq's improved security and stability since the sectarian fighting a few years ago that almost pulled the country into civil war.
Insurgents are seeking to belie Baghdad's better image, and officials expect more attacks as hundreds of dignitaries and journalists converge on the capital next week.
Two of the attacks Tuesday hit right outside the Green Zone where the summit will be held.
Last week, the government said Iraq would deploy an unprecedented number of security forces to protect the capital for the summit. An estimated 26,000 police and soldiers -- including more than 4,000 from Iraq's north and south -- are expected to be deployed in Baghdad.
But citizens and lawmakers have questioned whether Baghdad would be safe during the Arab meeting.
Extremists have launched large-scale attacks in Iraq every few weeks for nearly a year. The violence now is nowhere as frequent as it was during the tit-for-tat sectarian fighting a few years ago. But the attacks appear to be more deadly than they were before American military's withdrawal in late December.
The last widespread wave of attacks across Iraq, on Feb. 23, killed 55 people and wounded more than 225.
Iraqi government spokesman Ali al-Dabbagh on Tuesday announced a weeklong federal holiday in Baghdad, from March 25-31, when government offices will be shut down.
Officials also will impose a curfew in parts of Baghdad on March 29, when the Arab heads of state fly in, and try to curb violence by shutting off roads near the Green Zone and encouraging people to stay at home.