A wave of bomb attacks targeting Shiite pilgrims in Iraq killed 28 people and wounded 78 Monday, a day before the peak of the Ashura religious commemorations, security officials and medics said.

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

In Monday'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 told AFP, 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 Shiite 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 Shiite 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 Shiite 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 Shiite pilgrims in Latifiyah, 40 kilometres (25 miles) 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 Shiite pilgrims.

The Ashura commemoration ceremonies, which peak on Tuesday this year, 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 Shiite 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.

Shiites 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.

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

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

Last year was the first in which Iraqi forces were in sole charge of security during Ashura.

In previous years, Ashura has been a target for Sunni Arab extremists, who see the ceremonies as symbolically highlighting the split between Islam's two main branches.

Iraq's Sunni minority and Shiite majority engaged in a bloody sectarian conflict beginning in 2006 that left tens of thousands of people dead.

Now-executed dictator Saddam Hussein's Sunni-dominated regime barred the vast majority of Ashura commemorations throughout his rule until his overthrow in the 2003 US-led invasion.

Shiites make up around 15 percent of Muslims worldwide. They represent the majority populations in Iraq, Iran and Bahrain and form significant communities in Afghanistan, Lebanon, Pakistan and Saudi Arabia.

Monday's attack comes with less than a month to go before US troops are to have completed withdrawing from Iraq. Fewer than 10,000 US military personnel now remain in the country.

Violence has declined in Iraq since its peak in 2006 and 2007, but attacks remain common. A total of 187 people were killed in November, according to official figures.