Hizbollah and Amal are suspected of mounting the protest in a bid to undermine the inquiry, which recently issued an arrest warrant for an Amal member and ex-minister who was allegedly aware of the neglected nitrate store which sparked the explosion.
The 2020 explosion, one of the worst non-nuclear blasts in history, killed more than 200 people and devastated swathes of Beirut.
Later on Thursday, a number of gunmen from Lebanese militant groups fired hundreds of bullets at buildings and into the air in central Beirut. Some militants also fired RPG launchers into the air, apparently at random.
Lebanon is already facing dire fuel and electricity shortages, the latter often leaving entire neighbourhoods without any power for days on end. Reports of food poisoning have also significantly increased as shops are unable to keep their goods refrigerated.
Thursday’s sniper attack took place on the border between Christian and Shi’ite Muslim neighbourhoods of Beirut, and was a frontline in the Lebanese civil war, which began in Ain el-Remmaneh in 1975.
Hezbollah’s al-Manar TV said the gunfire had targeted protesters as they headed to the palace, while images posted on social media showed dozens of children hiding in the hallway of a school near the area.