BAGHDAD – A man with explosives strapped to his belt blew himself up in a crowd, bombers struck a southern city and gunmen sprayed fire on security checkpoints in attacks Monday that claimed nearly 100 lives in Iraq’s deadliest day this year.

Officials were quick to blame insurgents linked to al-Qaida in Iraq for the shootings in the capital, saying the militants were redoubling efforts to destabilize the country at a time of political uncertainty over who will control the next government.

“Al-Qaida is trying to … use some gaps created by some political problems,” Maj. Gen. Qassim al-Moussawi, spokesman for Baghdad’s security operations center, told Arabiya TV. “There are well-known agendas for the terrorist groups operating in Iraq. Some of these groups are supported regionally and internationally with the aim of influencing the political and democratic process inside Iraq.”

n The violence began before dawn in Baghdad in a series of attacks against checkpoints and patrols. Gunmen disguised as cleaners used weapons fixed with silencers to spray security forces with bullets. At least 10 people were killed.

But most of the day’s casualties were in two Shiite-dominated cities where wounded victims screamed their fury at the government for failing to protect them.

n The worst violence hit the Shiite city of Hillah, the capital of Babil province 60 miles south of Baghdad.

First, two parked car bombs near a textile factory exploded as workers were leaving the factory around midday, said Babil provincial police spokesman Maj. Muthana Khalid.

Then, as rescuers and workers were trying to help the injured, a suicide attacker with explosives strapped to his belt blew himself up in the crowd. At least 45 people were killed and dozens more injured, according to Khalid and al-Hillah hospital director Zuhair al Khafaji.

n In another Shiite city, the southern port of Basra, three bombs, including one that targeted a marketplace, killed at least 15 people, hospital and police officials said. Basra has been relatively quiet since the days when Shiite militias allied with Iran ruled the streets; al-Maliki, with heavy U.S. support, routed the militias in 2008.

n A pair of bombs struck the small town of Suwayrah, 25 miles south of Baghdad, killing 11.

n Three different bombings in the town of Abu Ghraib west of Baghdad killed at least six people.

n Twelve more were killed in five separate attacks stretching from the northern city of Mosul to the western city of Fallujah in Anbar province to the Shiite city of Musayyib south of Baghdad.