Iraq experienced its worst day of violence this year on Monday as 99 people died in a series of bombings and attacks across the country.

A pair of bombings in the southern city of Basra killed at least 15 people and injured dozens more, said an official who spoke on condition of anonymity.

Iraqis react to an explosion in Hillah in this image taken from TV on Monday. A suicide bomber blew himself up outside a textile factory in Hillah in a crowd that gathered after two cars bombings at the same location. (APTN/Associated Press)

The worst attack of the day took play in the Shia city of Hillah, where at least 45 people died in a triple bombing outside a textile factory.

The day's violence began earlier in the day in the capital city of Baghdad, where at least 10 people died in a series of attacks on police and army checkpoints.

In that attack, assailants wearing the uniforms of city-employed cleaners drove by the checkpoints and sprayed them with gunfire from weapons with silencers.

In Hillah, which is about 95 kilometres south of Baghdad, a suicide bomber ignited his explosives in a crowd of people helping victims of two earlier car bombings, said Babil provincial police spokesman Maj. Muthana Khalid.

About 140 people were wounded in the triple bombings.

"Terrified people were running in different directions," said Jassim Znad Abid, a taxi driver.

"I saw dead people, some burned and crying, wounded people on the ground that was covered with pools of blood. Dozens of wounded people asking for help were lying on the ground."

With files from The Associated Press