Iraq’s military said Tuesday multiple rockets were launched at a heavily fortified section of Baghdad where at least 22 people have been killed since violence erupted after powerful Shiite Muslim cleric Moqtada al-Sadr announced he would resign from politics.

Clashes continued overnight involving al-Sadr supporters after a day of violence Monday that included fighting with both Iraqi security forces and rival Shiite groups.

Iraq’s military announced a nationwide curfew and called on protesters to leave the Green Zone, the center of the international presence in Baghdad.

The violence broke out hours after al-Sadr announced he was withdrawing from politics because of the country’s political deadlock.

The cleric won the most seats in the October election, but not a majority. He withdrew all his lawmakers from parliament in June after refusing to form a coalition government with Iran-backed Shiite rivals.

Al-Sadr has insisted that the entire parliament be dissolved and early elections be held.

The stalemate has led to political uncertainty and volatility in the country. Al-Sadr’s followers have been staging a weekslong sit-in at parliament to press the cleric’s demands.

Al-Sadr has withdrawn from politics in the past only to later return to government. His critics have dismissed his latest move as an attempt to gain more power.

The Shiite cleric has a large following, having gained support by opposing both the United States and Iran.

The United Nations Assistance Mission in Iraq called Monday’s developments “an extremely dangerous escalation” of events in the country.

It called on “protesters to immediately leave” Baghdad’s International Zone and “to vacate all government buildings.”

Some information in this report came from The Associated Press, Reuters and Agence-France Presse.