BAGHDAD - A series of car bombings in Iraq struck five Shiite mosques as worshippers were emerging from Friday prayers, killing at least 23 people, officials said.

The attacks — four in Baghdad and one in the country's north — were the latest spectacular assaults staged by insurgents seeking to undermine the Shiite-led government's efforts to achieve security across the country.

There was no immediate claim of responsibility, but the bombings bore the hallmarks of al-Qaida's Iraq branch. The Sunni Muslim group, known as the Islamic State of Iraq, frequently uses car bombs, suicide bombers and coordinated blasts in an effort to sow fear among Shiites and erode their trust in the government of Prime Minister Nouri al-Maliki.

In the first blast in Baghdad, a parked car exploded in Baghdad's western Jihad neighborhood, killing seven worshippers and wounding 25, a police officer said. Another bombing in the eastern Qahira neighborhood killed four and wounded around 20, while another blast killed three more and wounded another 15 in the Zafaraniyah district. A fourth car bomb killed five people and wounded 14 in the northeastern Binook neighborhood.

Three health officials confirmed the causality figures. All officials in Baghdad spoke on condition of anonymity because they were not allowed to talk to the media.

In the northern city of Kirkuk, 290 kilometers (180 miles) north of Baghdad, a suicide bomber drove his explosive-laden car into a group of worshippers as they were leaving a mosque after Friday prayers, killing three people and wounding up to 70, according to police Col. Najat Hassan. A senior provisional health official, Sidiq Omar Rasool, confirmed the casualty figures in Kirkuk.

Also Friday, a roadside bomb struck a joint patrol north of Baghdad, killing an army officer and a police officer, a police official said. Seven others were wounded in the attacks in the town of Muqdadiyah, about 60 miles (90 kilometers) north of Baghdad, the official added on condition of anonymity because he was not allowed to talk to the media.

Violence has ebbed sharply since the peak of Sunni-Shiite fighting that pushed the country to the brink of civil war in 2006 and 2007, but Sunni insurgents still occasionally carry out high-profile attacks against Shiites, considering them to be heretics.

Friday is a particularly popular day for militants to undertake such attacks because of the rush of mostly men and boys who flock to the mosques throughout the country to hear traditional Muslim sermons and take part in communal prayers.

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Associated Press writer Qassim Abdul-Zahra contributed to this report.