BAGHDAD — Iraq’s highest religious authority backed the demands of anti-government protesters on Friday as security forces resorted to lethal fire against hundreds of demonstrators.

Prime Minister Adel Abdul Mahdi’s government is scrambling to quell a wave of demonstrations, and at least 41 people have been killed and more than 1,600 wounded since Tuesday, according to the country’s independent human rights commission. An address by the prime minister, aired Friday, did little to assuage frustrations on the street.

Crowds have swelled across Baghdad and much of southern Iraq as harsh police tactics have only hardened the resolve of protesters, who initially turned out to decry official corruption. The demonstrations, which appear to be leaderless, are coalescing around a demand for a wholesale change of what they describe as a broken system. Many protesters also have been denouncing Iranian influence in Iraq.

In a widely anticipated Friday sermon, Iraq’s most influential Shiite cleric, Grand Ayatollah Ali Sistani, urged the government to implement sweeping reforms and called on both sides to step back from the violence before it was “too late.” Sistani’s pronouncements have the potential to dampen or inflame the street protests. Hours after he spoke, another of the country’s most influential clerics, Moqtada al-Sadr, demanded the government’s resignation in the hope that it would preserve the protesters’ “blood.”

The unrest has mostly taken place amid an information blackout. Authorities have suspended Internet service across much of the country, and an indefinite curfew is in place.

In Baghdad, the anxiety on Friday was palpable. Streets were mostly eerily quiet, and families said they were stockpiling food. Prices rose steeply, and roads were cut with barbed wire. Where protests had taken place the night before, masked soldiers fanned out and helicopters circled low.

But near the city’s central Tahrir Square, violence worsened as security forces clashed with hundreds of protesters. The crowd was overwhelmingly young, jobless and male. Security forces, who largely fired bullets in the air in previous days, shot directly at the crowds on Friday, and snipers appeared to be positioned on the rooftops.

One man in his early 20s appeared to have been shot in the head, and his blood spooled out across the asphalt. Other victims were rushed toward ambulances.

Battered by years of conflict and mismanagement, Iraq’s economy is struggling to absorb thousands of young graduates into the job market. Corruption is rife and opportunities, when they arise, are often seen as the preserve of families with political connections. Most jarringly for many, there have been few improvements in the two years since Iraq’s security forces pushed Islamic State militants from cities they had occupied.

“Look at me, look at this blood,” shouted Karrar Alami, 22, near Tahrir Square, gesturing toward a dark-red stain he said came from the wounds of a close friend. “We fought the Islamic State for them, and all we wanted in return was a job. This is how they repay us.”

Abdul Mahdi came to power last year as a consensus prime minister, but promises to tackle corruption and unemployment have gone unfulfilled.

In a lackluster speech Friday, he described the nationwide curfew as “bitter medicine” and asked for patience, saying there were “no magical solutions.” In exercising crowd control, security forces were abiding by “international standards,” he said.

But a brief lifting of the Internet blackout to coincide with his speech sent another set of images flooding across social media. In nighttime videos from neighborhoods where security forces appeared to have little control, protesters held up spent bullet casings by the handful.

“There seems to be a calculation by those who are trying to protect the political system that there’s a level of violence that is acceptable,” said Renad Mansour, a research fellow at the London-based Chatham House think tank. “If you listen to what the protesters are calling for, it’s not about getting rid of Abdul Mahdi. It’s about calling for an end to the whole system. They’re fed up with the government’s inability to reform, and bringing in new faces won’t help.”

Iraq’s human rights commission said Friday that the government had yet to disclose the full extent of the week’s casualties and accused security forces of arresting wounded demonstrators at hospitals across the country.

Ali al-Bayati, the commission’s spokesman, said that 35 people had been detained from hospitals in the southern city of Nasiriyah and that arrests had also taken place inside facilities in Wasit and Diwaniyah.

In Baghdad’s Sheikh Zayed Hospital, a medic said that Shiite paramilitaries were monitoring the arrival of the wounded. In one instance, he said, gunmen had shot at an ambulance to prevent a patient from reaching the facility to undergo brain surgery.

Although Iraq’s Shiite militias are technically part of the state, they often operate as a parallel security force.

As night fell, ragged crowds of protesters carried photographs of friends killed or wounded days earlier. “They’re using snipers, and so this means war,” said Mustafa Saleh, 24. “They’re not the only one with weapons.”