Iraq's top leaders Sunday demanded the arrest of protesters who attacked lawmakers when they stormed parliament in the heavily fortified Green Zone in Baghdad.
Prime Minister Haider al-Abadi, parliament Speaker Salim al-Jabouri and President Fouad Massoum in a joint statement called the breach a "serious aggression against the state prestige."
On Saturday, thousands of followers of influential Shiite cleric Moqtada al-Sadr poured into the Green Zone and descended on parliament, protesting the delay in approving a cabinet of independents proposed by al-Abadi.
Hours later, the protesters left parliament, only to start an open-ended sit-in at a nearby square to push for long-delayed reforms.
"The aggressors must be brought to justice because what happened constitutes a flagrant violation of the constitution," Iraq's three top leaders said in the statement released by Massoum's office.
Al-Abadi inspected the parliament building late Saturday shortly after the demonstrators had left and checked the damage caused to some offices, state media reported.
He ordered authorities to arrest protesters who attacked security forces and lawmakers, and destroyed property during the breach, according to a statement from his office.
"They must be referred to court to get fair punishment," al-Abadi said.
The breach marked a dramatic escalation in the political crisis in Iraq, which is struggling against Islamist insurgents.
Security forces have an increased presence in the Green Zone, which houses government offices and foreign embassies, witnesses said Sunday.
No arrests have been reported among the protesters camping in the area.
For several months, Iraq has witnessed numerous demonstrations against corruption and inefficient public services.
In response, the Shiite prime minister proposed a package of major reforms, including the formation of a government of independent technocrats. But political blocs in parliament have thwarted the move.
Al-Abadi has warned that the current crisis can hamper the country's US-backed fight against the Islamic State extremist group, which controls key areas in Iraq's Sunni heartland.
In recent months, Islamic State has carried out a series of attacks in Iraq mainly targeting the country's Shiite community and security forces.
At least 30 people were killed and 55 wounded in a twin bombing in the mostly Shiite southern town of Samawa claimed by Islamic State.
The extremist group said in a statement circulated by its supporters online, that two suicide bombers detonated back-to-back car bombs in Samawa, around 300 kilometres south of Baghdad.
The attack was the second in two consecutive days to be claimed by Islamic State. The statement could not be independently verified.
Local officials said the attack involved a car bomb and another explosive device.
On Saturday, 24 people were killed in a car bombing targeting Shiite pilgrims in a Baghdad suburban area.
Islamic State, a radical Sunni militia, regards Shiites as heretics.