BAGHDAD: Iraqi troops opened fire on stone-throwing Sunni demonstrators in the country's restive west on Friday, leaving five dead in the first killings of protesters in more than a month of anti-government rallies.

The violence is likely to exacerbate tensions between the Shiite-led government and minority Sunnis angry over perceived second-class treatment and what they see as unfair policies targeting their sect.

Hours after the shooting, police said gunmen attacked an army checkpoint, killing two soldiers, in apparent payback for the earlier bloodshed. At least one army vehicle was set ablaze, and dozens of civilian gunmen were seen roaming the streets before local authorities imposed a curfew in the city.

Friday's protest was part of a wave of rallies that first erupted in Anbar province last month after the arrest of bodyguards assigned to Sunni Finance Minister Rafia al-Issawi, who comes from the area. Anbar is a former al-Qaida stronghold that saw some of the fiercest fighting against U.S. forces during the war.

The protesters are demanding the release of detainees and the cancellation of a tough counterterrorism law and other policies they believe overwhelmingly target Sunnis. Many link their cause with the broader Arab Spring and

are calling for the downfall of the government altogether.

Prime Minister Nouri al-Maliki's government has done little to crack down on the protests and has released hundreds of detainees in a concession to the protesters' demands. But he has also criticized some in their ranks for seeking to undermine the democratic process and exacerbate the country's sectarian divisions.

In a statement issued after Friday's shooting, al-Maliki urged government security forces to show restraint and avoid the use of force. He also called on protesters not to provoke the army.

At the same time, he suggested unruly protesters were to blame for the incident.

"Today, in a deliberate act, a group of misguided people attacked one of the army's checkpoints. They started their assault using rocks and then shooting followed, and this has caused causalities and a rise in tension that al-Qaida and terrorist groups are trying to take advantage of," al-Maliki said.

Sunni Arabs, who comprise some 15 percent of Iraq's 28 million population, were dominant under Saddam Hussein and formed the backbone of the insurgency that arose after majority Shiites rose to power following the U.S.-led invasion in 2003. Sectarian violence that once pushed the country to the brink of civil war has ebbed significantly and most American forces withdrew in December 2011.

Sunni cooperation, particularly from tribal leaders in Anbar, was key to the drop in violence. Increasing anger on view at the protests has raised fears of a rise in bloodshed.

Friday's outbreak of violence began about a kilometer (less than a mile) from a protest area in Fallujah, the birthplace of the insurgency as well as the U.S.-backed Sunni revolt against al-Qaida that helped quell the bloodshed, some 65 kilometers (40 miles) west of Baghdad, police officials said.

They said demonstrators grew angry after being held up at the army checkpoint, first shouting and then throwing rocks. The soldiers initially shot into the air in an effort to disperse the protesters, who eventually tried to storm the post, police said.

Ahmed Mahmoud, 16, a high school student who was among those delayed at the checkpoint, said the treatment protesters received this Friday was different than in the past.

"We take this road every week, and nobody used to stop us. But today, the soldiers stopped us and started to harass us," he said. "No Fallujah residents want the soldiers in our city. ... The army should get out. If they don't, these confrontations will continue."

Associated Press television footage taken at one point during the clashes showed protesters, some carrying Saddam Hussein-era Iraqi flags, pelting army Humvees with stones.

The video appears to show some soldiers aiming level with the protesters and shooting directly toward them,

while others fired into the sandy ground.

At least 23 protesters were wounded in the shooting, in addition to those killed, officials said. Medics at a hospital in Fallujah confirmed Friday's casualties. All officials spoke on condition of anonymity because they were not authorized to speak to the media.

Toby Dodge, a Middle East expert at the London School of Economics and author of a recent book on postwar Iraq, said Friday's shooting was likely the result of a miscalculation by the army rather than the deliberate start of

a wider crackdown.

"Middle Eastern armies are very bad at crowd control. ... The Iraqi army is really poorly disciplined. It has a real weakness with non-commissioned officers, like you'd have on those checkpoints," he said.

The clashes occurred as tens of thousands of demonstrators filled a major highway nearby, repeating a scene that has become common in areas across Anbar around midday Friday prayers.

Smaller rallies have been held in other predominantly Sunni parts of the country, and thousands of protesters have staged an ongoing sit-in along a highway connecting Baghdad to Jordan and Syria.

Sunni cleric Mohammed al-Dulaimi, who led the prayers at the Fallujah protest, urged demonstrators to show restraint and avoid further friction with the soldiers.

In his speech, he also accused al-Maliki's government of adopting policies that could divide the country.

"I tell the prime minister that he should stop neglecting our demands and stop violating our rights. ... Otherwise, the volcano will erupt," he said.

The wave of rallies in Iraq has been largely free of violence until Friday, though at least two demonstrators were wounded in Anbar last month when bodyguards and security forces protecting Sunni Deputy Prime Minister Saleh al-Mutlaq opened fire to disperse angry crowds.