Insurgents launched a wave of attacks across Iraq on Monday, primarily targeting Shia communities and pilgrims and killing at least 23 people, officials said.

The attacks appeared aimed at undermining security and confidence in the government by fomenting sectarian conflict. Overall violence has dropped since the nation neared a civil war several years ago, but attacks of a sectarian nature come almost daily, and government forces seem powerless to prevent them.

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Explosions killed at least 23 people and wounded more than 70 across Iraq on Monday, police said, underlining sectarian and ethnic divisions in the country. (Saad Shalash/Reuters)

The deadliest blasts on Monday were in the town of Musayyib, about 60 kilometres south of the capital, where militants planted bombs around two houses, one belonging to a police officer. Two women, two children and three men were killed in the pre-dawn explosions, a police officer said.

In Baghdad's Shia neighbourhood of Karrada, a parked car bomb went off next to a tent for Shia pilgrims making their way to the southern city of Karbala to mark the seventh century death of the Prophet Muhammad's grandson, Imam Hussein, a police officer said. Five were killed and 25 wounded, he said.

The explosion rattled nearby buildings and sent a thick plume of black smoke billowing into the air. Ambulances and police rushed to the scene in the busy downtown shopping district, and several helicopters hovered above.

That came hours after a parked car bomb exploded in a busy street in the city of Hillah where local government offices are located, killing three people and wounding 21, another police officer said. He said some Shia pilgrims were among the casualties, but he didn't say how many. Hillah is about 95 kilometres south of Baghdad.

Annual Shia gathering in Karbala

Two other Shia pilgrims were killed and 16 wounded in the town of Khalis, 80 kilometres north of Baghdad, when two bombs exploded simultaneously, another police officer said. In the town of Latifiyah, about 30 kilometres south of Baghdad, one pilgrim was killed and 11 wounded when two mortar rounds exploded nearby, another police officer said.

Six doctors confirmed the casualty figures. All officials spoke on condition of anonymity as they were not authorized to release information to reporters.

Also Monday, four policemen were killed in the northern city of Kirkuk while trying to defuse a bomb the centre of the city, according to police Col. Taha Salaheddin. Kirkuk is 290 kilometres north of Baghdad. The city is a focus of a power struggle among several sects and the Baghdad government.

Another a policeman was killed when a bomb hit a police convoy in the town of Tuz Khormato, 210 kilometres north of Baghdad, said the provincial spokesman of Salahuddin province, Mohammed al-Asi.

Although violence has ebbed since the height of the insurgency in the past, some groups presumed to be primarily Sunni extremists are still able to launch deadly attacks nationwide against government officials or civilians.

Shia pilgrims are one of their favourite targets. Each year, hundreds of thousands converge on the southern city of Karbala where the Imam Hussein, an important figure in Shia Islam, is buried. Many travel on foot, and the mass gatherings are frequently attacked, despite tight security.