An Iraqi soldier and people inspect the site of a bomb attack in Kerbala.

A truck bomb in a crowded market in the central Iraqi city of Diwaniya killed at least 25 people on Tuesday, the latest victims of a spike in nationwide violence, medical and security officials said.

“At least 25 people were killed and around 70 wounded when a bomb blew up in a truck parked in the central market” at around 10.15am (07.15 GMT), a police colonel told AFP on condition of anonymity.

A hospital source in the city, 160 kilometres south of Baghdad, confirmed receiving 25 dead.

Shortly afterwards authorities imposed a curfew across the city of about 440 000 people.

Women and children were among the victims of the attack that hit the main vegetable market of Diwaniya, where 15 shops and stalls were destroyed, the officials added.

The blast came just hours after near-simultaneous car bombs targeting Shi'a pilgrims on the outskirts of the central shrine city of Karbala killed four people.

The 7.00am (04.00 GMT) attack struck the village of Freyha, 10 kilometres east of Karbala, ahead of commemoration ceremonies on Friday for the birth of a key figure in Shi’a Islam.

“There were four killed and 13 wounded by two car bombs at around 7.00am, east of Karbala,” provincial police spokesman Lieutenant Colonel Ahmed al-Hasnawi said.

A medical official in Karbala, speaking on condition of anonymity, put the toll at four dead and 33 wounded.

Karbala is frequented by Shi’a pilgrims as it is the site of shrines to Imam Hussein and his half-brother Abbas, both central figures to Shi’a Islam.

Friday's ceremonies are to mark the birth of another figure, known as the 12th imam.

North of the capital in Taji, a policeman was among two people killed in simultaneous bomb attacks, an interior ministry official said. A hospital official said three people died in the blasts.

The first bomb exploded closely followed by a second blast as police rushed to the scene, the ministry official said, adding that 14 people were also wounded, eight of them policemen.

Another bomb attack in the town of Tuz Khurmatu north of Baghdad killed a policeman and wounded another, an officer and a local doctor said.

The violence comes amid a spike in attacks in Iraq, with the country suffering a wave of unrest in June that left at least 282

people dead according to an AFP tally, although government figures said 131 Iraqis died.

While violence in Iraq has declined dramatically since its peak in 2006-2007, attacks remain common across the country. -