Three suicide bombers detonated explosives belts among Shiite pilgrims in Iraq on Thursday, killing at least 36 people, while militants shot dead a family of five, officials said.

The deadliest attack hit the Dura area of south Baghdad, where a bomber targeted pilgrims at a tent where they are served food and drinks on their way to the shrine city of Karbala, killing at least 20 people and wounding at least 40.

Among those killed in the blast was Muhanad Mohammed, a journalist who had worked for both foreign and Iraqi media, one of his sons told AFP.

He was the seventh journalist to be killed in the country in less than three months.

Two more bombers targeted pilgrims in areas south of Baghdad -- one in Yusifiyah, killing eight people and wounding at least 32, and another in Latifiyah, killing at least eight people and wounding at least 18.

At Yarmuk Hospital in Baghdad, wounded people were rushed in on gurneys for treatment. Those injured included children and an old woman whose face was covered in blood.

One distraught man in the lobby of the surgery department repeatedly struck himself in the face with both hands, overcome with grief.

In the street outside, empty wooden coffins sat on vehicles, while people cried and screamed over the loss of loved ones.

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

The throngs of pilgrims on the roads make for an easy target, and they have been hit by a series of attacks in the past few days.

On Wednesday, a suicide bomber targeted Shiite pilgrims in Khales, north of Baghdad, killing five people and wounding 10.

The toll would likely have been higher were it not for the selfless actions of a policeman who embraced the bomber just before the attack, in an effort to shield others from the blast.

On Tuesday, two attacks against pilgrims in and near Baghdad killed at least eight people, and on Monday two car bombs targeting pilgrims south of the capital killed at least 24.

Also on Thursday, militants dressed in army uniforms attacked the house of an anti-Al-Qaeda militiaman in the Abu Ghraib area, west of Baghdad, killing him, his wife and their three children.

The Sahwa militia are made up of Sunni Arabs who joined forces with the United States from late 2006, helping to bring about a significant reduction in violence.

They are often targeted by Sunni militants, who consider them traitors.

Violence in Iraq has surged this year to levels not seen since 2008, when the country was just emerging from a brutal sectarian conflict.

More people were killed in the first eight days of this month than in all of December last year.

And more than 6,550 people have been killed since the beginning of 2013, according to AFP figures based on security and medical sources.

Analysts say that widespread discontent among Iraq's minority Sunni Arab community is a major factor fuelling the surge in unrest, while the civil war in neighbouring Syria, which has bolstered extremist groups, has also played a role.

And though the government has made some concessions aimed at placating Sunni Arabs, including freeing prisoners and raising the salaries of Sahwa fighters, underlying issues remain unaddressed.