Iraqi Prime Minister Nuri al-Maliki ordered a shakeup of senior security officers on Tuesday as violence killed 21 people, the latest in a wave of unrest that has cost more than 380 lives in May.

"After consultation with security officials, the commander-in-chief of the armed forces, Prime Minister Nuri al-Maliki, today (Tuesday) issued orders ... for changes in the operations commands and the leadership of the divisions," a statement on Maliki's website said.

One of those changes was to sack Staff Lieutenant General Ahmed Hashem, the head of the Baghdad Operations Command, which is responsible for security in the capital, a senior official told AFP.

The shakeup comes a day after Maliki said he would change the country's security strategy as well as top personnel.

"We are about to make changes in the high and middle positions of those responsible for security, and the security strategy," Maliki told reporters on Monday.

Iraq is struggling to contain a wave of unrest that has killed 387 people so far this month, including 21 who died on Tuesday.

A car bomb near a mosque in Abu Ghraib, west of Baghdad, killed six people and wounded at least 18, officials said.

Dozens of mosques have been attacked so far this year, including two Shiite places of worship in Hilla, south of Baghdad, where bombs killed 13 people on Monday.

Near Baquba, north of Baghdad, gunmen killed a Sunni couple in their home but spared their three children, while two roadside bombs at a market near the city killed three people and wounded seven, police and a doctor said.

And clashes between police and gunmen near Baquba killed two police and wounded six, according to the same sources.

In Tarmiyah, also north of the capital, clashes between soldiers and gunmen, and a suicide bombing killed three soldiers and wounded at least seven, security and medical officials said.

Two car bombs exploded in a Shiite Turkmen neighbourhood of the northern town of Tuz Khurmatu, killing three people and wounding 44, and causing extensive damage to 10 houses, police and a doctor said.

And two roadside bombs detonated in a sheep market in the northern city of Kirkuk, killing two people and wounding 25, officials said. The explosions also killed a number of sheep, seen lying at the site.

Tuz Khurmatu and Kirkuk are part of a swathe of territory that Kurdish leaders want to incorporate in their autonomous region in the north over the strong objections of the federal government -- a dispute diplomats and officials say is a major threat to the country's long-term stability.

The attacks came a day after violence killed more than 60 people across Iraq.

Tensions are festering between the government of Maliki, a Shiite, and Sunnis who accuse authorities of marginalising and targeting their community, including through wrongful detentions and accusations of involvement in terrorism.

Protests broke out in Sunni areas of Iraq almost five months ago.

While the government has made some concessions aimed at placating the protesters and Iraqi Sunnis in general, such as freeing prisoners and raising the salaries of Sunni anti-Al-Qaeda fighters, underlying issues have yet to be addressed.

Violence in Iraq has fallen from its peak in 2006 and 2007 but attacks are still common, killing more than 200 people in each of the first five months of this year, according to AFP figures.