Militants killed at least eight Shiite pilgrims in and around Baghdad on Tuesday, after car bombs targeted others the day before, Iraqi security officials said.

A suicide bomber detonated explosives among pilgrims walking south of Baghdad, killing four, while militants in a car threw hand grenades at pilgrims in the capital, killing at least four others.

The two attacks also wounded at least 27 people.

The violence came after two car bombs targeted Shiite pilgrims south of the Iraqi capital on Monday night, killing at least 24 people and wounding over 50.

Hundreds of thousands of people, many of them on foot, make pilgrimages to the holy city of Karbala during the 40 days after the annual commemoration marking the death of the Prophet Mohammed's grandson, Imam Hussein.

The 40th day, known as Arbaeen, falls on December 23 this year.

Sunni militants, including those linked to Al-Qaeda, frequently target members of Iraq's Shiite majority, whom they consider to be apostates.

Interior ministry spokesman Saad Maan meanwhile said in an online statement that there had not been "any explosion or aggression against pilgrims in the Mahmudiyah area," where other sources said the suicide bombing took place.

Maan had said in an earlier statement that security forces killed a suicide bomber who was "attempting to target pilgrims... in the Mahmudiyah area."

Maan also asserted that the grenades thrown in the Baghdad attack were defused without causing any casualties.

The Iraqi government frequently seeks to downplay deaths from the rampant violence plaguing the country, releasing "official" death tolls that are often far lower than those given by other sources.

A spokesman for the security command responsible for Baghdad meanwhile issued two emailed statements, one of which confirmed that soldiers had killed a suicide bomber south of the capital, and another saying that security forces had killed five militants in clashes.

Violence in Iraq has reached a level this year not seen since 2008, when the country was just emerging from a period of brutal sectarian killings.

More people died in violence in the first eight days of this month than in the whole of last December, and over 6,500 people have been killed since the beginning of 2013, according to AFP figures based on security and medical sources.