Thousands of Shiite pilgrims headed on foot to a north Baghdad shrine on Thursday to commemorate the death of a revered Shiite imam, undaunted by waves of attacks that killed 72 people a day earlier.

Routes leading to Kadhimiyah neighbourhood, site of the shrine of Imam Musa Kadhim, the seventh of 12 Shiite imams who died in 799, were closed to all traffic except emergency vehicles, AFP journalists said.

Pilgrims wound under a blistering sun through the streets in their thousands, repeating religious chants, some beating their chests in a sign of mourning for the imam.

Tents along the way provided the pilgrims with free food and water.

In the Utayfiyah area of north Baghdad, long lines of pilgrims, many wearing green headbands and some carrying green flags, the colour of Islam, were seen marching toward the shrine.

Vast crowds of chanting pilgrims were also seen walking through Karrada in central Baghdad, where a bomb on Wednesday blasted the pilgrims' food tents, killing 16 people, damaging cars and scattering human remains across the street.

Another car bomb exploded on the outskirts of Kadhimiyah on Wednesday, killing seven people, leaving a hole two metres (yards) deep in a street, damaging cars and destroying a number of makeshift houses.

"This is the sixth year I have come ... I left home around 2:00 am and I feel so good now," said Hussein Murawih, 17, who walked from Suwayrah, some 60 kilometres (40 miles) southeast of Baghdad.

"We just came to tell the terrorists that we are against you. We are not afraid of the explosions or of terrorism. Visiting Imam Kadhim is a great thing because we want to express condolences to the imam."

Another pilgrim also brushed off Wednesday's killings.

"The explosions mean nothing for us. It is not something new. Even if 20 car bombs exploded every day, does that mean we will stop walking to the imam? No," said Salam Jaber, 27.

"I have been walking for five days," said Jaber, who came from the town of Muwafaqiyah, some 180 kilometres (111 miles) southeast of Baghdad.

Coordinated attacks took place right across Iraq on Wednesday, leaving a total of 72 people dead and more than 250 wounded, and marking the deadliest day in the country in almost 10 months.

Shiite pilgrimages were prohibited under the rule of Saddam Hussein, who was executed in 2006 after being overthrown by a US-led invasion

Along with the security forces, the Shiite majority in Iraq has been a main target of Sunni Arab armed groups since the 2003 fall of Saddam's Sunni-dominated regime.

Violence across Iraq has declined dramatically since the 2006-2007 peak but attacks remain common, especially in Baghdad. A total of 132 Iraqis were killed in May, official figures show.