Thousands of Iraqis gathered Wednesday at the site of a Baghdad bombing that killed at least 250 people to mourn the dead and express solidarity with those stricken by the blast.

A suicide bomber detonated an explosives-rigged vehicle in Baghdad's Karrada district early Sunday as it teemed with shoppers ahead of the holiday marking the end of the holy Muslim fasting month of Ramadan, sparking infernos in nearby buildings.

The street running between the charred remains of buildings burned in the attack claimed by the Islamic State (IS) jihadist group was packed with people on Wednesday, some carrying Iraqi flags, others holding candles.

Many wept and beat their chests in mourning for the dead.

"We came from all the areas of Baghdad to stand in solidarity with the people of Karrada and the martyrs of Karrada," said Haider Mohammed Hassan, one of those gathered at the bomb site.

"The Christian community in Iraq, especially in Baghdad, gathered to visit this sorrowful site," Adel Kanna said.

"I ask God to give patience and fortitude to the families of the martyrs," he said.

Some Christians held pictures of the Virgin Mary, while uniformed members of Asaib Ahl al-Haq carried flags of the Shiite militia force.

The blast sparked widespread anger among Iraqis, some of whom have accused the government of not doing enough to protect them.

And it has overshadowed what would normally be a joyful holiday for Muslims, instead turning it into a time of mourning and grief.

IS overran large areas north and west of Baghdad in 2014, but Iraqi forces have since regained significant territory from the jihadists.

In response to the battlefield setbacks, the group has hit back against civilians, and experts have warned there may be more bombings as the jihadists continue to lose ground.