BEIRUT — Heavy gunfire broke out Thursday in Beirut during a protest organized by the Hezbollah group against the judge leading the probe into last year’s blast in the city’s port. At least six people were killed and dozens wounded in the most violent street fighting in the Lebanese capital in years.

The exchanges of fire along a former front line from the 1975-90 civil war involved pistols, automatic rifles and rocket-propelled grenades, and were reminiscent of that conflict. Gunfire echoed for hours, and ambulances rushed to pick up casualties. Snipers shot from buildings. Bullets penetrated apartment windows in the area. Schools were evacuated and residents hid in shelters.

The chaos raised the specter of a return to sectarian violence in a country already embroiled in multiple crises, including one of the world’s worst economic crises of the past 150 years.

It was not clear who started the shooting, which began shortly after the start of the protest organized by the Iran-backed Hezbollah and its Shiite allies from the Amal Movement against Judge Tarek Bitar, who is leading the investigation into last year’s massive port explosion. Hezbollah and its allies accuse the judge of singling out politicians for questioning, most of them allied with Hezbollah.

Tensions over the port blast have contributed to Lebanon’s many troubles, including a currency collapse, hyperinflation, soaring poverty and an energy crisis leading to extended electricity blackouts.

Officials from both Shiite parties, including Hezbollah leader Hassan Nasrallah, had attacked Bitar for days, accusing him of politicizing the investigation by charging and summoning some officials and not others. They want him removed.

None of Hezbollah’s officials have so far been charged in the 14-month investigation.

The probe centers on hundreds of tons of ammonium nitrate that were improperly stored at a port warehouse that detonated on Aug. 4, 2020. The blast killed at least 215 people, injured thousands and destroyed parts of nearby neighborhoods. It was one of the largest non-nuclear explosions in history and further devastated the country already beset with political divisions and financial woes.

Bitar is the second judge to lead the complicated investigation. His predecessor was removed following legal challenges.

On Thursday, shortly before the planned protest, an appeals court turned down a request to remove Bitar from his post filed by two lawmakers who are defendants in the case, both of them allies of Hezbollah.

The calls for the judge’s removal upset many who considered it blatant interference in the work of the judiciary.

The right-wing Christian Lebanese Forces mobilized supporters Wednesday evening after Hezbollah and Amal called for the protest at the Justice Palace, located on the former front line separating predominantly Muslim and Christian areas of Beirut. Videos circulating on social media Wednesday night showed supporters of the Christian Lebanese Forces marching in the streets, carrying large crosses.

In a statement Thursday, the two Shiite groups said their protesters came under fire from snipers deployed over rooftops.

The army also said protesters came under fire, but later in the evening said an “altercation and exchange of fire” occurred as the protesters were headed to the Justice Palace.

The violence unfolded while U.S. Undersecretary of State for Political Affairs Victoria Nuland was in town, meeting with Lebanese officials. Her schedule was slightly thrown off by the action on the streets.

Nuland later told an airport news conference that an impartial judiciary is the guarantor of all rights, in apparent criticism of Hezbollah. “The Lebanese people deserve no less, and the victims and the families of those lost in the port blast deserve no less,” she said. “Today’s unacceptable violence makes clear what the stakes are.”

As the clashes erupted, an Associated Press journalist saw a man open fire with a pistol and gunmen shooting in the direction of protesters from a balcony. Several men fell immediately and bled on the street. The army sent patrols to the area following the gunfire between the Muslim and Christian sides of the capital.

The Lebanese Red Cross said at least 30 people were wounded. One of the dead, a mother of five, was shot in the head.

Four projectiles fell near a private French school, Freres of Furn el Chebbak, causing panic. In scenes reminiscent of the civil war, students huddled in the central corridors. Smoke covered the neighborhoods that saw relentless gunfire.

The shooting subsided around four hours later, after army troops were deployed.

Youssef Diab, a journalist who specializes in court affairs, said the protest was meant as a show of force and a message that Hezbollah and Amal control the street. What happened showed them that they are not the only ones who control the street.

“There is another street, and confronting it could blow up the situation in a big way,” Diab said.

In a statement, Prime Minister Najib Mikati appealed for calm and urged people “not to be dragged into civil strife.”

Beirut resident Haneen Chemaly, who heads a local group that provides social services, hid with her 6-month-old baby in her building’s shelter and then at her neighbors’ home. She accused Lebanon’s leaders of steering the country into civil war, saying it’s “the last card they have to use.”

“They have (driven) us into bankruptcy, devastation and now they are scaring us with the specter of civil war,” she said.

Michel Younan, a resident of Ain el-Remeneh neighborhood, inspected his car, which had its windows and doors broken in the fighting. “There were protests and then suddenly gunfire began … Shooting, RPGs, everything,” he said. “Isn’t this a shame? They brought us back to the days of the war.”

The clashes could derail Mikati’s month-old government even before it begins tackling Lebanon’s economic meltdown.

A cabinet meeting was canceled Wednesday after Hezbollah demanded urgent government action against the judge. One Hezbollah-allied minister said he and other Shiite cabinet members would stage a walkout if Bitar isn’t removed, further complicating Mikati’s mission.

BEIRUT — Armed clashes erupted Thursday during a protest in Beirut by the militant group Hezbollah and its allies against the lead judge probing last year’s massive blast in the city’s port. Five people were killed and 16 were injured, Lebanon’s interior minister said.

Interior Minister Bassam Mawlawi said many of the casualties were shot by snipers from buildings.

“This is a very dangerous sign,” Mawlawi told reporters. “No one can take this.”

The exchanges of fire involving snipers, pistols, Kalashnikovs and rocket-propelled grenades were a serious escalation of tension over the domestic probe, and the worst armed clashes since 2008, when the Shiite Hezbollah briefly overran parts of Beirut.

It was not immediately clear how Thursday’s clashes began. The Hezbollah group and its Shiite allies from the Amal Militia had called for a protest near the Justice Palace, along a former civil war front-line between Muslim Shiite and Christian areas.

In a statement Thursday, the two groups said their protesters came under fire from snipers deployed over rooftops in the Tayouneh area.

Gunfire echoed in the capital for several hours and ambulances, sirens wailing, rushed to pick up casualties. Snipers shot from buildings. Bullets penetrated apartment windows in the area. Four projectiles fell near a private French school, Freres of Furn el Chebbak, causing panic, a security official said, speaking on condition of anonymity because he was not authorized to speak to the press.

The students huddled in the central corridors with the windows open to avoid major impact, in scenes reminiscent of the 1975-90 civil war. Smoke covered the neighborhood where intense gunfire was relentless. A car caught fire, while a blaze was reported in a lower floor where residents were stuck and called for help.

The violence unfolded while U.S. Undersecretary of State for Political Affairs Victoria Nuland was in town, meeting with Lebanese officials. Her schedule was slightly thrown off by the action on the streets.

The demands for Bitar’s removal and calls for protest upset many.

The right wing Christian Lebanese Forces mobilized supporters Wednesday evening after Hezbollah and Amal called for the protest at the Justice Palace, located in a Christian area. Videos circulating on social media showed supporters of the Christian Lebanese Forces marching in the streets, carrying large crosses.

A journalist with The Associated Press saw a man open fire with a pistol during the protest, as well as gunmen shooting in the direction of protesters from the balcony of a building. Several men fell immediately from the gunfire and bled on the tarmac. The army deployed heavily and sent patrols to the area to search for the gunmen, following the exchanges of gunfire between the Muslim and Christian sides of the capital.

A staffer at the emergency room at al-Sahel hospital said they received three bodies and 15 people who were injured. One of the dead, a woman, had received a bullet to her head. Two of the 15 injured were in critical condition.

In a statement, Prime Minister Najib Mikati appealed for calm and urged people “not to be dragged into civil strife.”

The probe centers on hundreds of tons of ammonium nitrates that had been improperly stored at a port warehouse that detonated on August 4, 2020, killing at least 215 people, injuring thousands and destroying parts of nearby neighborhoods. It was one of the largest non-nuclear explosions in history and has further devastated the country already roiled by political divisions and unprecedented economic and financial meltdown.

Bitar, the second judge to lead the complicated investigation, has come up against formidable opposition from Lebanon’s powerful Hezbollah group and its allies who accuse him of singling out politicians for questioning, most of them allied with Hezbollah.

None of Hezbollah’s officials have so far been charged in the 14-month-old investigation.

The shooting continued even after army troops deployed to the area Thursday, with the sound of exchange of fire ringing over their heads. Residents and civilians in the area were ducking to avoid the shooting, some screaming: “Some martyrs on the ground!” People pulled one man who was apparently shot and down, away from the line of fire. Others pulled another body away.

In some videos circulating online, some men were chatting: “Shiite Shiite” on the streets, as residents were running from the gunfire.

Haneen Chemaly, a resident of Furn el-Chebbak and mother of a 6-month old girl, said she first moved to the corridor before running to the shelter because the sound of gunfire was terrifying from her 10th-floor apartment.

“I did it for my child,” she said. “I don’t know what is happening. I can just hear the sound of gunfire.”

She said there was no electricity for her to follow on TV what was going on. So she knew nothing of the situation on the ground and opted for safety. After spending some time in the shelter, she moved to the first floor to stay with her neighbors away from the fire.

“I know there was so much mobilization from the night before, all predicting that a war would erupt,” Chemaly, who heads a local NGOs that provides social services. Civil war erupting “is the last card they have to use. They have (driven) us into bankruptcy, devastation and now they are scaring us with the specter of civil war.”

The armed clash could derail the country’s month-old government of Prime Minister Najib Mikati even before it begins tackling Lebanon’s unprecedented economic crisis.

A Cabinet meeting was canceled Wednesday after Hezbollah demanded urgent government action against the judge. One Hezbollah-allied minister said he and other Cabinet members would stage a walkout if Bitar isn’t removed.