Iraqis today mourned more than 200 people killed in a Baghdad suicide bombing claimed by the Islamic State group and accused the government of not doing enough to protect them.

The search continued for bodies at the site of the attack, which ripped through the Karrada district early on Sunday as the area was packed with shoppers ahead of this week's holiday marking the end of the Muslim fasting month of Ramadan.

Prime Minister Haider al-Abadi announced efforts to address longstanding flaws in Baghdad security measures following the blast, which came a week after Iraqi forces recaptured the city of Fallujah from IS.

But on the streets of Baghdad, Iraqis were angry at the government's inability to keep residents safe, even as its forces push IS back outside the capital.

"I swear to God, the government is a failure," said a woman who gave her name as Umm Alaa, who lost her apartment in the attack.

IS "tactics are changing. Why does the Iraqi government have fixed tactics?" a man said at the site of the bombing, criticising the government's "stupid checkpoints" and use of fake bomb detectors.

As the country marked three days of national mourning, security and medical officials told AFP the number of dead from the attack had risen to at least 213. More than 200 were also wounded, they said.

Map of central Baghdad locating Sunday's deadly suicide car bombing in the Karrada district of the city.

In Karrada, a young man lit a candle on a staircase leading to the basement of one charred building, adding to dozens of others left by mourners at the site of bombing, which sparked infernos in nearby buildings.

Digging through ashes

Down the stairs, young men dug through the ashes using shovels and their hands, searching for those still missing following the blast.

Black banners bearing the names of victims -- including multiple members of some families -- hung from burned buildings, announcing the date and locations where their funerals would be held.

Abadi was met with an angry response when he visited the site of the bombing on Sunday, with one video showing men throwing rocks at what was said to be the premier's convoy, while a man could be heard cursing at him in another clip.

But the premier struck a conciliatory tone.

"I understand the emotional feelings and actions that occurred in a moment of sadness and anger," Abadi said in a statement.

IS claimed the attack in a statement saying it was carried out by an Iraqi as part of "ongoing security operations".

The jihadist group said the blast targeted Iraq's Shiite Muslim majority, whom the Sunni extremists consider heretics and frequently attack in Baghdad and elsewhere.

Bombings in the capital have decreased since IS overran large areas north and west of Baghdad in June 2014, with the jihadists apparently more concerned with operations elsewhere.

But the group has struck back against Iraqi civilians after suffering military setbacks, and in May, Baghdad was rocked by a series of blasts that killed more than 150 people in seven days.

With thousands of vehicles moving in and out of the city each day, such bombings are difficult to prevent.

'Cowardly and heinous act'

But there are also flaws in security measures in the city, especially the use of fake bomb detectors at checkpoints years after the man who sold them to Iraq was jailed for fraud in Britain.

Abadi announced a series of changes to security measures following the Sunday bombing, including scrapping the fake detectors.

He also ordered the deployment of scanning devices at entrances to Baghdad to be sped up, directed that security personnel be banned from using mobile phones at checkpoints, and called for increased aerial reconnaissance and coordination among security forces.

But soldiers and policemen still carried the fake detectors at some checkpoints in central Baghdad on Monday, saying the order to stop using them had not yet been passed down.

The bombing came after Iraqi forces completely recaptured Fallujah, a city 50 kilometres (30 miles) west of Baghdad, a week ago.

Anti-government fighters seized Fallujah in early 2014 and it later became one of IS's main strongholds in the country.

IS's defeat there was compounded by a devastating series of air strikes targeting jihadist forces as they sought to flee the Fallujah area that officials said killed dozens and destroyed hundreds of vehicles.

Sunday's attack was widely condemned, with the UN Iraq envoy Jan Kubis calling it a "cowardly and heinous act of unparalleled proportions."