Supporters of prominent Iraqi Shia leader Muqtada Al-Sadr stormed Baghdad's Green Zone on Saturday before forcing their way into the parliament building where they broke windows and smashed furniture.
Pro-Sadr demonstrators overran barriers set up around the heavily-fortified Green Zone, which houses a number of vital Iraqi state institutions and foreign diplomatic missions.
The Iraqi army has since responded by declaring a state of high alert in the capital and sealing all entrances into the city.
Speaking at a press conference in the city of Najaf, located some 160 kilometers (99.4 miles) south of Baghdad, al-Sadr voiced his rejection of what he described as "a political system that fails to take the popular will into account."
He also announced the suspension of the activities of his "Ahrar" political bloc, which holds 34 seats in parliament, asserting that Ahrar MPs would refrain from participating in upcoming assembly sessions.
Corrupt officials, he declared, "are still preventing the reform of Iraq's government. Cabinet ministers… do not represent us; they represent the government."
Al-Sadr added: "There are enormous pressures on [Prime Minister Haidar] Al-Abadi by certain sectarian forces. We want to get rid of them [i.e., sectarian forces] and leave the final word to the people."
Meanwhile, Al-Abadi in an official statement later Saturday said: "Baghdad is under control of the security forces."
He warned protesters against infringing on public properties.
Iraqi President Fuad Masum urged the protesters to remain calm, abide by the country's laws, not harm any parliamentarians and evacuate the building.
Masum also urged the prime minister, the head of the political blocs and the parliament speaker to make necessary arrangements concerning the ministries, implement administrative reforms and fight against corruption.
Iraqi Parliament Speaker Salim Al-Jubouri also called on al-Sadr to rein in his supporters.
"We will not hesitate to take appropriate decisions with our partners to recover our country from the chaos," Al-Jubouri said, adding: "Daesh is waiting for security vulnerability and we should not allow it."
Also, Deputy Parliament Speaker Aram Sheikh Mohammed, who got stuck in the parliament building as protesters it, was rescued.
In a written statement, Mohammed said he had been stuck inside for six hours and added that a few more Kurdish parliament members still remain trapped in the building.
Meanwhile, a scheduled session of parliament to vote on nominees for a proposed Cabinet lineup was postponed to May 10 after lawmakers failed to meet the required quorum.
In recent months, al-Sadr supporters have staged several mass demonstrations near the Green Zone to reiterate longstanding demands for sweeping government reform.
Last month, the firebrand Shia cleric's supporters surrounded several government ministries in Baghdad to press for their demands.
Iraq has been embroiled in a deepening political crisis since March, when al-Sadr loyalists began staging protests in the capital with a view to pressing Al-Abadi to appoint a government of "technocrats" untainted by corruption or sectarian affiliations.
The crisis escalated further earlier this month when MPs refused to allow Al-Jabouri to chair a scheduled assembly session, accusing him of failing to summon the prime minister to answer corruption allegations.
Iraq ranks 161st out of 168 countries on Transparency International's "corruption perceptions index".