BAGHDAD: Two car bombs in the southern Iraqi city of Samawah on Sunday killed 31 people and wounded dozens, the latest in a series of large attacks claimed by the Islamic State group as the country grapples with a worsening political crisis.

The attacks came the day after thousands of anti-government protesters poured into Baghdad's heavily guarded Green Zone and stormed parliament, the culmination of months of protests by followers of an influential Shiite cleric demanding wide-ranging political reforms.

A police officer said two parked cars filled with explosives were detonated within minutes of each other around midday in Samawah, the first near government offices and the second at an open-air bus station less than a kilometre away.

At least 52 people were wounded in both explosions, and the police official said the death toll was expected to rise. A medical official confirmed the casualty figures. Both officials spoke on condition of anonymity as they were not authorised to release information.

IS claimed the bombings in an online statement, saying they were carried out by suicide attackers targeting police. It was not immediately possible to reconcile the competing claims.

Earlier on Sunday, Prime Minister Haider al-Abadi ordered authorities to arrest and prosecute protesters who attacked security forces, lawmakers and damaged state property after breaking into the Green Zone.

Followers of influential cleric Muqtada al-Sadr tore down blast walls and poured into the Green Zone and parliament building on Saturday.

Videos on social media showed a group of young men surrounding and slapping two Iraqi lawmakers as they attempted to flee the crowd, while other protesters mobbed lawmakers' motorcades.

Jubilant protesters were also seen jumping and dancing on the parliament's meeting hall tables and chairs and waving Iraqi flags. No one was seriously wounded. The protesters eventually left the parliament Saturday night and rallied at a nearby square.

Al-Sadr and his supporters want to reform the political system put in place following the US-led invasion in 2003, in which entrenched political blocs representing the country's Shiites, Sunnis and Kurds rely on patronage, resulting in widespread corruption and poor public services. The major blocs have until now stymied al-Abadi's reform efforts.

On Sunday, protesters vowed to continue their sit-in inside the Green Zone until their demands are met.

“We are fed up, we are living a humiliated life,” Rasool Hassan, a 37-year old father of three told The Associated Press from inside the Green Zone. “We'll leave here only when the corrupt government is replaced with another of independent technocrats that serves the people not the political parties,” Hassan added.

“We need new faces, not the old ones,” said Shatha Jumaa, a 58-year old surgeon. Jumaa, who identified herself as a secularist, said she wanted the current government dissolved and replaced by a small interim administration whose job would be to amend the constitution and to prepare for an early national election.

Also on Sunday, the United Nations said at least 741 Iraqis were killed in April due to ongoing violence, a sharp decline from the previous month. In its monthly report, the UN mission to Iraq put the number of civilians killed at 410, while the rest were members of the security forces. A total of 1,374 Iraqis were wounded that month, it added.

In March, at least 1,119 people were killed and 1,561 wounded.

The capital, Baghdad, remains the worst-hit area, with 232 civilians killed and 642 wounded in April, followed by the northern province of Ninevah, which is almost entirely controlled by the Islamic State group, with 72 killed and 30 wounded.

“It pains us to see the continuing bloodletting and loss of life, particularly among civilians who are paying a high price as a result of bombings and the armed clashes,” UN envoy Jan Kubis said.