BAGHDAD — Supporters of populist Shiite cleric Moqtada al-Sadr celebrated into the night Monday after initial results from Iraq's parliamentary elections revealed his party as the biggest winner amid losses for Iranian-backed groups.

In Baghdad, young men cruised the streets of the capital in pickup trucks, blasting music and flashing victory signs. Under the famous Freedom Monument in the capital’s Tahrir Square, once the epicenter of mass protests that triggered this week’s early elections, a jubilant crowd waved emerald flags and pumped photos of the cleric aloft.

Initial results suggested that former prime minister Nouri al-Maliki and the parliament’s Sunni speaker, Mohamed al-Halbousi, had also performed strongly as a powerful Iranian-aligned bloc fell behind.

The losses of the Iranian-backed parties that have long dominated politics in the country could have serious implications, especially as many of their leaders seemed set to contest the results.

The spokesman for the Iranian-backed Kataib Hezbollah militia group, Abu Ali al-Askari, described the vote as the “biggest fraud and circumvention against the Iraqi people in modern history.”

Eighteen years after the U.S.-led invasion, this election had in many ways become a referendum on the political system that it installed. Government posts are divided along religious and ethnic lines, and parties empowered in the process have siphoned millions of dollars from state coffers.

On Monday, most Iraqis stayed home, either actively refusing or too frustrated to endorse that reality with their votes. Iraq, after all, is a country in crisis. Decades of corruption have left public services on their knees. Unemployment stands around 14 percent as the country’s population swells by a million each year.

Election campaign posters promising a change had decked Iraq’s thoroughfares for weeks. But by mid-Monday, many of those with metal frames had disappeared — scavenged by poor families for scrap.

“Today is a day of victory,” Sadr said Monday, in a speech from a silver lectern. “Now it’s time for the people to live without occupation, wars, militias, terrorism, kidnappers and fearmongering.”

The cleric’s movement also has an armed wing, which has been accused of kidnapping and killing critics, among them a 17-year-old boy on the eve of the election.

On Monday, the official turnout from the previous day’s vote was announced at 41 percent. The real number is probably lower because the government’s official figure was calculated as a proportion of registered voters, rather than eligible voters as a whole.

The public vote, held Sunday, was triggered by mass protests in 2019. They began as a call for an end to corruption. When security forces cracked down, killing hundreds, it turned into a revolt against the entire system, including Iranian-linked militias that now play a powerful role in the country.

Prime Minister Mustafa ­al-Kadhimi took office last year after those protests felled his predecessor, Adel Abdul Mahdi, and on Sunday, he hailed the ballot as a fulfillment of “our promise and our duty.”

In a news conference Tuesday, the head of a European Union observation mission, Viola von Cramon, said that the vote had been “largely peaceful and orderly.” But she also emphasized that public perceptions about the reach of armed groups may also have affected the vote.

“The potential of party-affiliated non-state armed actors to intimidate both the electorate and candidates may have had [an] effect on voters’ choice and turnout,” she said.

For the most part, Iraqis had viewed the ballot as the rubber stamp for the status quo. “We’ve voted for years, and what have they given us?” said Hassan, a young graphic designer from Baghdad who asked that his full name be withheld. “These parties all have armed wings, and they’ve been killing us, whether through negligence or with their guns.”

The results rollout Monday was chaotic. At a 3 p.m. news conference, the head of Iraq’s election commission, Jalil Adnan, said that initial results had been counted and would be available online. He ended the session abruptly.

By nightfall, Sadr’s party appeared to have increased its presence in parliament by more than 20 in the 329-seat body, handing it the biggest bloc of about 75 seats and the largest say over government formation.

Maliki’s and Halbousi’s parties appeared to be roughly neck and neck in second with about half as many. In the country’s Kurdish region, the Kurdish Democratic Party prevailed amid low voter turnout and widespread apathy.

Among the night’s poorest performers was an Iranian-aligned political grouping, Fatah, which appeared to have lost more than half of its seats.

Iran holds far-reaching sway in Iraq, but it has also drawn the ire of a growing section of the population that says it is tired of the country’s politics being shaped by external forces. The protests’ slogan was: “We want a homeland.”

Election experts also pointed to a difference in strategy between the Sadrists and Iranian-linked parties. Iraq’s elections were held under a new law that divided the map into smaller campaign districts. Where the Sadrists had run a sophisticated campaign choosing districts into which to concentrate resources, Fatah had overcommitted, they said, and lost out as a result.

Fatah representatives were not reachable by phone Monday night, but Hadi al-Amiri, who leads the Fatah coalition, described the results as “fabricated.”

“Whatever the cost, we will defend the votes of our candidates,” he said.

There were also surprise wins for parties linked to Iraq’s protest movement. Despite scores among them having faced threats, abductions or assassinations by Sadrist and Iranian-aligned paramilitaries, representatives of the Imtidad movement appeared to have won about 10 seats in Baghdad and the country’s southern provinces.

Candidates had been hard to recruit, said Wissam Kawkab, a spokesman for the movement. “For those who stepped up, we sat them down at the start, and we told them: ‘In this project, your life may be in danger, you may be assassinated like the others.’ 

“These seats, they’re a start.”

With results almost finalized, protracted negotiations over the shape of Iraq’s next consensus government will follow. The process has often taken months.

“Within the Shiite house, there has been a shift in the power balance, and this is going to mean that negotiations are going to be to a certain degree more difficult because at the end of the day, politics in Iraq is based on consensus,” said Lahib Higel, a researcher with the Crisis Group.

“Somehow Sadr will need to find a way to be pragmatic if he wants to keep the political peace,” she said.