23 dead, 100s injured. What is happening in Iraq?

23 people have died and hundreds have been injured in violent clashes in Iraq after powerful Shiite cleric Moqtada al-Sadr said he would quit politics, reported AFP.

This announcement led to his loyalists storming the government palace and fighting with rival groups. Reminding us of the Sri Lanka crisis, many rushed into the palace, a key meeting place for Iraqi heads of state and foreign dignitaries, reported AP.

Iraq's military has announced a nationwide curfew, and the caretaker Prime Minister has suspended cabinet sessions and called for peace.

The violence: Street fighting erupted soon after Sadr's announcement and it got more intense in the next few hours.

• Saraya Salam, a militia aligned with Sadr, clashed with the Popular Mobilization Forces (PMF) security group. Many shells fell in the high-security Green Zone, which houses government buildings and diplomatic missions, reported AFP.

• The PMF is an umbrella group composed of state-sanctioned paramilitary groups, the most powerful of which are aligned with Sadr's rivals in the Iran-backed political camp, reported AP.

• Some of the violence was between the Peace Brigades, a militia loyal to Sadr, and members of the Iraqi military.

What led to the clashes: Sadr's party got the highest numbers of seats in October parliamentary elections but didn't reach the majority mark. Sadr's movement won 73 out of the assembly's 329 seats. He has refused  to negotiate with his Iran-backed Shiite rival and now his decision to quit has created a political crisis in the country and clashes have erupted between different Shiite groups, reported AP.

• Shiites were oppressed in Iraq under Saddam Hussein's rule but now they are among themselves over power and influence. Sadr, a nationalist, wanted reforms in the country and he has a huge following of people who hail from Iraq's poorest sectors of society and have been kept out of the political system for a long time.

• His followers want the parliament to be dissolved and fresh elections to be conducted without the participation of Iran-backed Shiite groups, which they see as responsible for the status quo, reported AP.

The Iran influence: Since the last two decades, Iran has had a big role to play in Iraq. Be it politics, helping Iraq in rehabilitation post US invasion or uniting the Shiite population, Iran has always been there.

But since the parliamentary elections last year, there has been a big struggle between two Shiite groups in the country. One side which is led by Sadr has nationalist ideology and doesn't want to be seen too close to Iran. The other side, the Coalition Framework, led by former Prime Minister Nouri al-Maliki is known to be close to Iran, reported The Wall Street Journal.

Why Sadr decided to quit: Sadr announced his withdrawal from politics in a tweet and ordered the closure of all his party offices on Monday.

Sadr's announcement seems to be a reaction to the retirement of Shiite spiritual leader Ayatollah Kadhim al-Haeri and his appeal to his followers to throw their allegiance behind Iran's Ayatollah Ali Khamenei, rather than the Shiite spiritual centre in Iraq's holy city of Najaf, reported AP.

The move, according to AP, was a blow to al-Sadr, who despite harbouring ambitions to be a religious authority lacks the scholarly credentials to be an ayatollah (a high-ranking religious leader among Shiite Muslims).