This is an archived article and the information in the article may be outdated. Please look at the time stamp on the story to see when it was last updated.

BAGHDAD (AP) — Tens of thousands of Iraqis gathered in a Baghdad suburb on Friday to perform a mass prayer called for by an influential Shiite cleric, sparking fears of instability amid a deepening political crisis that has followed the country’s national elections.

Followers of Moqtada al-Sadr arrived in the capital from across the country, filling up Sadr City’s al-Falah Street — the main thoroughfare that cuts across the populist figure’s key bastion of support. Worshippers carried Iraqi flags and wore white scarves, typically donned by his supporters.

They stood under the scorching sun and chanted religious slogans.

The event is expected to be among the largest gatherings of al-Sadr’s followers after the U.S.-led invasion that toppled Saddam Hussein in 2003, but it also carries a message to al-Sadr’s political rivals of his ability to mobilize the Iraqi street and de-stablize the country.

Al-Sadr, who won the most seats in the October national elections, withdrew from the government formation last month, following eight months of stalemate. In line with his orders, the members of his parliamentary bloc resigned.

Al-Sadr had sought to form a government with Sunni and Kurdish allies that excluded Iran-backed parties lead by his long-time rival, former Prime Minister Nouri al-Maliki.

The surprise move shocked his opponents and his supporters alike, sparking fears of more unrest and street protests if al-Maliki forged ahead with government formation plans that excluded al-Sadr. If the political crisis extends to August, it will be the longest that Iraq has gone without a government since elections.

The threat of mass demonstrations is a well established tactic by al-Sadr that has proven successful in the past. Many fear the mass prayer service on Friday could evolve into protests.

In a tweet on Thursday ahead of the prayer, al-Sadr said the choice to protest was up to his followers, and that “I support them if they want to stand up for reform.” Many considered that a veiled threat to his rivals.

The prayer service is also an ode to al-Sadr’s father, cleric Muhammad Sadiq al-Sadr, from whom he derives much of his support base. The elder al-Sadr had held Friday prayer service in defiance of the Saddam regime in the 1990s. He was was assassinated in 1999.