Tens of thousands of Iraqis have attended a mass prayer in a Baghdad suburb which was called by an influential Shiite cleric.

The event has sparked 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 area of support.

Worshippers carried Iraqi flags and wore white shrouds, typically donned by his supporters.

The event was considered a show of force from the cleric whose party won the highest number of seats in the October national elections but withdrew after failing to form a government with Sunni and Kurdish allies in Iraq’s power-sharing system.

Followers stood under the scorching sun and chanted religious slogans.

Mr Al-Sadr’s representative Sheikh Mahmoud al-Jiyashi read aloud a speech from the cleric during the service that reiterated calls to disband armed groups — an indirect reference to Iran-backed Iraqi militia groups affiliated with his rivals.

Ahmad Kadhim, 17, was among the worshippers. He said he was disappointed Mr Al-Sadr himself did not appear at the service. “I would have been happy just to see him, but this wish did not come true,” he said.

By capitalising on fears that the mass prayer could turn into protests, Mr Al-Sadr sent a potent message of his authority and power.

The event was among the largest gatherings of his followers since the US-led invasion that toppled Saddam Hussein in 2003.

But more importantly, it carried a message to Mr Al-Sadr’s political rivals of his ability to mobilise the Iraqi street and destabilise the country.

In a tweet on Thursday ahead of the prayer, Mr Al-Sadr said the choice to protest was up to his followers.

“I support them if they want to stand up for reform,” he wrote. Many considered that a veiled threat to his rivals.

Mr 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.

He 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 Mr Al-Maliki forged ahead with government formation plans that excluded Mr 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 Mr Al-Sadr that has proven successful in the past.

In 2016, his supporters repeatedly targeted the Green Zone, a heavily fortified area housing Iraq’s government buildings and foreign embassies, even storming parliament complex and attacking officials.