The Sunni-led armed rebellion by the Islamic State group (ISIS) bombarded Iraq's Shiite community with attacks Monday, killing at least 33 people, reports Yahoo! News.

A suicide bomber detonated himself as Shiite worshippers left midday prayers at a Baghdad mosque, killing 17 people and wounding 28, law enforcement said.

In the holy city of Karbala, nearly 55 miles south of Baghdad, three separate car bombs went off simultaneously in commercial districts and parking lots near government offices, killing at least 16 people and wounding 41.

The Baghdad and Karbala attacks happened one day after a suicide bomber struck a Shiite mosque in the Iraqi capital, killing 28 people.

Prime Minister Haider al-Abadi, who took office in September, met Monday with top Shiite cleric Grand Ayatollah Ali al-Sistani in Najaf, the city south of Baghdad where the reclusive cleric lives. The spiritual leader greatly influences Iraq's Shiite majority. The meeting carried symbolic importance because al-Sistani has openly criticized politicians about how they run the country.

Al-Sistani gave his approval to the new government and its battle against ISIS.

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

While no group has claimed responsibility for the attacks, officials believe it was a calculated effort by the Islamic State group to strike in the hearts of Iraqis and further pressure Iraq's new Shiite-led government.

This summer's barrage by ISIS has caused Iraq its worst crisis since the U.S. military withdrew at the close of 2011.

ISIS has seized control of land in northern and western Iraq, creating a proto-state between Iraq and Syria where it dispenses its own tyrannical form of Islamic law, or Shariah.

Since August, U.S. fighter and bomber aircraft have launched over two dozen airstrikes against the militants as Iraqi and Kurdish ground forces work to reclaim the seized territory, according to the American military.