Hundreds of followers of an influential Shi’ite cleric have stormed Iraq’s government palace shortly after he announced he was withdrawing from politics, further deepening an unprecedented political crisis.

Mr Muqtada al-Sadr’s followers on Monday stormed the Republican Palace, a key meeting place for Iraqi heads of state and foreign dignitaries.

On July 30, they stormed the parliament building to deter Mr al-Sadr’s rivals from forming a government.

Iraq’s military swiftly announced a city-wide curfew for civilians and vehicles on Monday to quell rising tensions and the possibility of clashes.

Mr al-Sadr’s protesters filled lavish waiting rooms in the palace and chanted slogans in support of the cleric.

They had earlier scaled the concrete barriers leading to the palace and had pulled down barriers leading to the palace gates.

Iraq’s military called on the protesters to withdraw immediately from the Green Zone and to practise self-restraint ‘‘to prevent clashes or the spilling of Iraqi blood,’’ according to a statement.

‘‘The security forces affirm their responsibility to protect government institutions, international missions, public and private properties,’’ the statement said.

In a tweet, the cleric said he was withdrawing from politics and ordered the closure of his party offices.

It is not the first time Mr al-Sadr has announced his retirement from politics, but many fear it could spur more escalation.

Mr al-Sadr’s statement on Monday was a reaction to the retirement of Shi’ite spiritual leader Ayatollah Kadhim al-Haeri, who counts many of Mr al-Sadr’s supporters as followers.

The previous day, al-Haeri announced he would be stepping down as a religious authority and called on his followers to support Iran’s Ayatollah Ali Khamenei, not the Shi’ite spiritual centre in Iraq’s holy city of Najaf.

The move was a blow to Mr al-Sadr. In his statement he said al-Haeri’s stepping down ‘‘was not out of his own volition’’.

Mr al-Sadr won the largest share of seats in the October elections but failed to form a majority government, leading to what has become one of the worst political crises in Iraq in recent years.

His bloc later resigned from parliament and Mr al-Sadr has demanded that parliament be dissolved and early elections held.