BAGHDAD (BLOOMBERG/AFP) - Iraq declared a state of emergency in Baghdad after supporters of Shi'ite Muslim cleric Moqtada al-Sadr stormed Parliament, the Interior Ministry said.

Mobile-phone video footage broadcast on Iraqi news channel al-Sharqiya showed hundreds of al-Sadr's supporters inside the legislature on Saturday (April 30). Al-Sadr earlier on Saturday accused lawmakers of sectarianism in their selection of ministers and ordered his bloc to withdraw from the Parliament session where members were preparing to finish voting on a new Cabinet.

Jubilant crowds invaded the main session hall, shouting slogans glorifying their leader and claiming that they had rooted out corruption. The capital was already on high alert for a major Shi'ite pilgrimage, participants in which were targeted in a bombing that killed 23 on Saturday, but extra security measures were taken after protesters stormed the Green Zone.

"You are not staying here! This is your last day in the Green Zone," shouted one protester as thousands broke in.

Besides the Parliament compound, the restricted area in central Baghdad houses the presidential palace, the prime minister's office and several embassies, including those of the United States and Britain.

Protesters pulled down several slabs of the heavy concrete blast walls that surround the Green Zone to create an opening and also climbed over the barrier, an AFP journalist said.

They then headed to Parliament, where some rampaged through the building and broke into offices, while others shouted "peacefully, peacefully" and tried to contain the destruction, another AFP reporter said.

Security forces were present but did not confront them. Protesters also moved into the nearby compound of the secretary general of Prime Minister Haider al-Abadi's office.

The US Embassy is monitoring the situation, it said in an e-mailed statement, adding that reports that embassy personnel are being evacuated are inaccurate. The highly fortified Green Zone houses most of the country's ministries and foreign embassies.

"Under the Vienna Convention, all diplomatic missions are protected by the host country's security forces," it said. "We have full confidence that the Iraqi Security Forces will meet its obligations."

Iraqi Prime Minister Haider al-Abadi, who has pledged to give minority Sunnis and Kurds a bigger role in the Shi'ite-dominated government, has faced resistance to an effort to replace politicians in key roles with technocrats.

He is also under fire for his handling of a financial crisis and charges of government corruption. Parliament canceled its session earlier this month after a failed vote on whether to retain its embattled speaker.

Some six hours after the Green Zone was stormed and despite the chaos, Mr Abadi issued a statement claiming the situation in Baghdad was "under the control of the security forces" and urging protesters to return to "designated protest areas".

Tear gas was used against protesters but violence did not escalate further, with both sides mostly seen fraternising.

An AFP photographer said members of the Sadrist militia group Saraya al-Salam were eventually seen directing protesters to leave the Parliament building after nightfall.

Protesters earlier pulled barbed wire across a road leading to one of the Green Zone exits, effectively preventing some scared lawmakers from fleeing the chaos.

They also attacked and damaged several vehicles they believed belonged to lawmakers.

Inside the main hall where lawmakers failed to reach a quorum earlier in the day, protesters sat in the MPs' seats taking "selfies" and shouting slogans.

One protester called a friend on his mobile: "I am sitting in (parliament speaker) Salim al-Juburi's chair, I have a meeting, we'll talk later."

"We are the ones running this country now, the time of the corrupt is over," said another, as crowds filled rooms throughout the building.

US officials including President Barack Obama have expressed concern Iraq's leaders remain mired in sectarian divisions that may undermine the fight against Islamic State in Iraq and Syria (ISIS).

Protesters reached the Cabinet headquarters inside the Green Zone, storming the general secretariat of the cabinet building, al-Sumaria reported, citing security officials. Security has been boosted around the central bank, the Interior Ministry said in an e-mailed statement.

The United Nations Assistance Mission for Iraq said it was "gravely concerned" by Saturday's developments and urged political leaders to work together to restore security in the country.

"The mission condemns the use of violence, including against elected officials, and urges calm, restraint and respect for Iraq's constitutional institutions at this crucial juncture," it said in an e-mailed statement.

Parliament failed to reach a quorum on Saturday after approving some of Mr Abadi's ministerial nominees earlier in the week.

The Green Zone unrest started as al-Sadr ended a news conference in the Shi'ite holy city of Najaf during which he condemned the political deadlock.

He had threatened to have his supporters storm the Green Zone last month, but did not order them to enter the area in his Saturday address.

The politicians "refused to end corruption and refused to end quotas", al-Sadr said, adding that he and his supporters would not participate in "any political process in which there are any type... of political party quotas".

Key government posts have for years been shared out based on political and sectarian quotas, a practice demonstrators want to end.

Mr Abadi's efforts to change the system have been opposed by powerful political parties that rely on control of ministries for patronage and funds.

According to Interior Ministry officials, the main entrances to Baghdad were temporarily closed, and measures were taken to protect the central bank and the airport.

Security forces had already been on high alert as tens of thousands of Shiite faithful converged on the city for an annual commemoration.

A car bomb that exploded earlier Saturday in the Nahrawan area near Baghdad killed at least 23 people and wounded at least 38, security and medical officials said. It struck a road used by pilgrims walking to the shrine of Imam Musa Kadhim in northern Baghdad, officials said.

ISIS, which considers Shiites to be heretics, claimed the attack and said it was carried out by a suicide bomber who detonated a vehicle laden with three tonnes of explosives.

Kadhim, the seventh of 12 imams revered in Shi'ite Islam, died in 799 AD. The pilgrimage has in recent years turned into a huge event that brings the capital to a standstill for days.