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BAGHDAD, July 4 (Xinhua) -- Iraq began on Monday a three-day national mourning for victims of Sunday's car bombing attacks in the capital city of Baghdad, as the death toll rises to 166.

An Interior Ministry source said at least 165 people were killed and 225 others wounded in a suicide bomb attack in Karrada-Dakhil district in southern Baghdad. Another one was killed in a separate car bombing in a market in northeastern Baghdad.

The Karrada-Dakhil bombing is the bloodiest attack this year in the country, where the army is fighting Islamic State militants.

The busy commercial district in southern Baghdad was hit by a car bomb at about 1:00 a.m. local time (2200GMT) on Sunday when a suicide bomber detonated his explosive-laden pickup truck outside a shopping center.

The three-floor building was destroyed, when many people were inside. Many of the victims were women and children, the source said. Rescuers said the explosion and the following huge fire killed all members in some families.

Prime Minister Haider al-Abadi announced three days of national mourning for the victims after he visited the blast site on Sunday. His convoy was attacked by dozens of angry residents who accused the government of failing to protect its people.

Local resident Mohammed Musa said: "now we demand a solution from the government, because since 2003 to 2016 we have been uncomfortable, we are in a difficult situation. And those people, all of them lost their money, property and lives and other things. Everything is gone."

As the commander-in-chief of Iraqi forces, Abadi ordered an intensification of security measures on the entrances of Baghdad and in other Iraqi provinces.

Sunday's powerful blast set fire to the shopping center and four nearby buildings while many shops and stalls were charred and destroyed, as well as dozens of civilian vehicles at the scene. The fire was put out in the afternoon and rescue operations continued till night.

Dozens of rescue workers, firefighters and civilians were removing debris and burned wreckage from dawn to the evening, looking for survivors and bodies.

The attack happened when many families and young people were in the crowded thoroughfare where many shoppers were preparing their families for Eidul-Fitr scheduled to start on Tuesday, which marks the end of the holy month of Ramadan.

Meanwhile, another car bomb went off in a market in northeastern Baghdad, leaving one dead and five wounded, the source added.

The death toll could rise as many wounded are in critical condition.

The bloody bombings have been claimed by the Islamic State (IS) group which said that one of its suicide bombers detonated his car bomb at a crowd of Shiite people in the predominantly Shiite district of Karrada-Dakhil, according to a statement posted online, which could not be independently verified.

During his visit to the explosion site in Karrada on Sunday morning, Abadi vowed to punish those behind the attacks, according to a statement issued by his office.

"The terrorist groups carried out such desperate deadly attacks as a result of being crushed in the battlefield," the statement said, referring to the government's recent victory of retaking Fallujah city from IS in the country's western province of Anbar.

Abadi also sent his condolences to the families of the victims and promised that "victory over these terrorist groups is very close."

The Iraqi government announced victory of retaking Fallujah, one of the last two strongholds of IS in Iraq, late last month, after almost a month of military operations.

The army is expected to be deployed to the northern Nineveh province, preparing to launch attacks against Mosul city, the country's second biggest city that fell into IS control two years ago.

In a statement issued on Sunday, Iraqi President Fuad Masoum condemned the deadly bomb attacks and called on the security forces to "take urgent measures to totally eliminate the sleeper terrorist cells and arrest the perpetrators."

"The sleeper terrorist cells are seeking to avenge the defeat of terrorist Daesh (IS) in Fallujah and other regions of the country," he said.

The IS has frequently targeted security forces and areas where crowds of people gather, including markets, cafes and mosques, across Iraq.

Observers said there could be more attacks against military targets and civilians in the future as the army advances to the last IS stronghold of Mosul.

Iraq has been hit by a wave of violence since the IS terrorist group seized large parts in Iraq's northern and western regions since 2014.

A report by the United Nations Assistance Mission for Iraq estimated that 662 Iraqis were killed and 1,457 others wounded in acts of terrorism, violence and armed conflict in June this year across Iraq.