BEIRUT — At least six people were killed Thursday and more than 30 injured as heavy gunfire broke out ahead of a demonstration in the Lebanese capital Beirut.

Authorities said it was an attack on protesters who were going to take part in the demonstration called by Hezbollah to demand the removal of a judge leading a probe into the deadly August 2020 port blast.

Interior Minister Bassam Mawlawi told a press conference that some of the victims had head injuries, suggesting they were shot by snipers. He called the events, “a very dangerous sign.”

Prime Minister Najib Mikati urged a halt of clashes to avoid further escalations and sectarian strife.

President Michel Aoun also discussed the situation over the phone with Mikati, the defence and interior ministers and the army chief.

The Lebanese Red Cross confirmed six deaths during the clashes.

Mawlawi said snipers and gunmen "shot people in the head," while four B7 rockets were fired into the air, in the worst violence the crisis-ridden capital has seen in over 10 years.

At least 30 people have been wounded, according to the Lebanese Red Cross.

Hundreds of supporters of Iran-backed Hezbollah and its main Shia ally, Amal, were marching toward the city's Palace of Justice when shots were fired at the protesters from an unknown location, forcing demonstrators and journalists to take cover, according to an army statement and local broadcasters.

There are multiple local reports of snipers shooting at demonstrators from the rooftops of buildings in the area. Local TV and social media videos also showed masked protesters firing what appeared to be AK-47s from behind street barriers and garbage dumps, apparently shooting back at the gunmen, and black smoke rising from one of the nearby buildings.

In a statement Thursday, Lebanon's military, which deployed extensively to the scenes of the gunfire, said it will shoot any armed person in the areas where the clashes are taking place and called for people to vacate the streets.

Eyewitnesses reported hearing rocket fire, and smoke was seen billowing from inside buildings that appeared to have been fired at. The epicenter of the violence, Tayouneh, is close to the birthplace of Lebanon's 1975-1990 civil war, and has raised the specter of further violence in the crisis-ridden country.

"It's clear that those who fired at the protesters were organized armed groups who have been planning this attack since yesterday," one high-ranking Hezbollah official told CNN. "We will not fire back. They want to drag us into civil strife and we do not want to sow civil strife."

In a joint statement, Hezbollah and Amal called "for calm" among their supporters on the streets.

The statement said the protesters had been the target of direct fire from snipers who were on the rooftops of the buildings opposite, followed by intense shooting 15 minutes before the official start of the demonstration.

They added that the attacks aim to "drag the country into deliberate civil strife" and called on the army to intervene to identify and arrest the perpetrators.

Hezbollah has been a staunch opponent of Tarek Bitar, the popular judge who is leading the Beirut blast investigation and has sought the prosecution of high-level officials. This week, the judge issued an arrest warrant against lawmaker Ali Hassan Khalil, a top Amal official and former finance minister.

Bitar has also issued arrest warrants against MP Nouhad Machnouk, an ally of former Prime Minister Saad Hariri and an ex-interior minister.

Since his appointment in February, Bitar, who also heads Beirut's criminal court, has sought top political and security officials for questioning in the Beirut blast probe. He is the second judicial investigator to head the investigation. The first judge tasked with handling the probe was dismissed after two ex-ministers charged in the investigation successfully filed a motion for his removal.

Several legal petitions by officials being prosecuted to dismiss Bitar have been unsuccessful.

During a televised speech on Monday, Hezbollah leader Hassan Nasrallah chastised the judge, accusing him of being "politicized." — Agencies