At least three people were killed and many more injured 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, according to the National News Agency.

The exchanges of fire involving snipers, pistols, Kalashnikovs and rocket-propelled grenades were a dangerous escalation of tensions over the domestic probe.

Gunfire echoed in the capital and ambulances rushed to the scene, sirens wailing. 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.

The protest outside the Justice Palace was called for by the powerful Hezbollah group and its allies who are demanding the removal of Judge Tarek Bitar.

It was not immediately clear what triggered the gunfire, but tensions were high along a former civil war front-line between Muslim Shiite and Christian areas.

The right wing Christian Lebanese Forces mobilized supporters Wednesday evening after Hezbollah and its allies 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 one 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. At least two men were seen injured and bleeding. 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.

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

Hundreds of tons of ammonium nitrates that had been improperly stored at a port warehouse 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.

The army then began firing at the crowd. The streets quickly became deserted, with only sounds of bullets. Shops were shut down.

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.