A wave of bomb attacks targeting Shia pilgrims in Iraq have killed 28 people and wounded 78, a day before the peak of the Ashura religious commemorations.

It was the bloodiest day in Iraq since 27 October, when at least 32 people were killed and 71 wounded in twin blasts in Baghdad.

In today's deadliest attack, a car bomb blasted pilgrims in the Neel area north of Hilla south of Baghdad, in central Iraq, security officials said.

"We received 16 bodies and 45 wounded," Dr Mohammed Ali of Hilla hospital, and a Hilla police first lieutenant confirmed that toll.

The police officer also said that a car bomb exploded in the centre of Hilla near Shia pilgrims, killing one person and wounding three.

A medical source in another hospital in Hilla said that it had received one body and 20 wounded.

Baghdad was also hit by bomb attacks against Shia pilgrims, with at least 10 people killed and 30 wounded.

"Eight people were killed and 18 wounded by a roadside bomb targeting a convoy of pilgrims in the Urr neighbourhood," a police source said.

That toll was confirmed by a medical source at the Imam Ali hospital in Sadr City, who said that "we received eight bodies and 18 wounded from an explosion in the Urr neighbourhood."

A medical source at Al-Kindi hospital said the hospital had "received two bodies and eight wounded from an explosion in Mashtal" in eastern Baghdad.

An interior ministry official said that attack was also aimed at Shia pilgrims, but gave a toll of three dead and eight wounded.

The official also said that four people were wounded by another roadside bomb targeting pilgrims in Zafraniyah in central Baghdad.

And a roadside bomb against Shia pilgrims in Latifiyah, 40km south of Baghdad, killed another person, a police source said.

The interior ministry official also said that two roadside bombs in the Qahira area of northern Baghdad wounded four civilians, while another bomb in the north of the capital wounded two others.

Those attacks did not target Shia pilgrims.

The Ashura commemoration ceremonies, which peak tomorrow, mark the killing of Imam Hussein, the grandson of the Prophet Mohammed, by armies of the caliph Yazid in 680 AD.

Tradition holds that the revered imam was decapitated and his body mutilated. His death was a formative event in Shia Islam.

During the Ashura commemorations, mourners demonstrate their ritual guilt and remorse at not defending Hussein by beating their chests, flaying themselves with chains or cutting their scalps during processions.

Shias also gather at night during the commemorations to listen to stories about Hussein's family and other companions who were killed prior to his death on the 10th day of Muharram, the first month of the Islamic Hijra calendar year.

Some two million Shia pilgrims completed rituals in the holy city of Karbala in 2010, amid heavy security for fear of attacks.

18 pilgrims were killed during the Ashura rituals last year, according to police.