Iraq's top Shiite cleric on Monday gave his support to the new government battling the Islamic State group as militants unleashed a wave of deadly attacks on the country's majority Shiite community, killing at least 43 people.

The blitz by the militants this summer plunged Iraq into its worst crisis since U.S. troops left at the end of 2011. While there was no claim of responsibility for Tuesday's attacks, they seemed likely calculated by the group to sow fear among Iraqis and keep pressure on the new Shiite-led government in Baghdad.

Prime Minister Haider al-Abadi, who took office last month, met Monday with top Shiite cleric Grand Ayatollah Ali al-Sistani in the southern city of Najaf. He said after their talks that al-Sistani welcomed the recent formation of the government that Al-Abadi now leads.

The spiritual leader wields considerable influence among Iraq's Shiite majority, and the meeting carried symbolic significance because al-Sistani has shunned politicians in recent years to protest how they run the country.

"We have a long and hard mission ahead of us," al-Abadi told reporters after emerging from the meeting with the cleric, who is believed to be 86 years old. "One of the missions is related to security. We need arms and we need to reconstruct our security forces."

Al-Sistani lives in the Shiite holy city of Najaf, 100 miles south of Baghdad, and rarely appears in public.

The day's attacks killed dozens in Baghdad and the Shiite holy city of Karbala.

In the capital, the bomber blew himself up among Shiite worshippers as they were leaving a mosque in a central commercial area after midday prayers Monday. That blast killed at least 17 people and wounded 28, a police officer said.

In Karbala, four separate car bombs went off simultaneously, killing at least 26 people and wounding 55, another police officer said. The city, about 55 miles south of Baghdad, is home to the tombs of two revered Shiite imams and the site of year-round pilgrimages. The explosives-laden cars were parked in commercial areas and parking lots near government offices, the officer added.

Medical officials confirmed the casualty figures. All officials spoke on condition of anonymity as they were not authorized to talk to media.

The attacks in Baghdad and Karbala, the latest in relentless assaults that have challenged the Shiite-led government, came a day after a suicide bombing targeted another Shiite mosque in the Iraqi capital, killing 28 people.

The latest attacks bore the hallmarks of the Islamic State group, which has recently claimed several other large bombings in Baghdad and elsewhere, particularly in Shiite areas.

The militants have captured large chunks of western and northern Iraq, carving out a proto-state on both sides of the Syria-Iraq border and imposing its own harsh interpretation of Islamic law. Since August, U.S. warplanes have been carrying out air strikes against the group as Iraqi and Kurdish security forces work to retake territory it has seized.