Lebanese Prime Minister Najib Mikati announced that Friday will be a day of mourning for the victims of the violence in Beirut.

"All administrations, public institutions, municipalities, public and private schools will be closed," he said Thursday. 

Six people were killed and at least thirty were wounded Thursday in armed clashes between rival groups that included an exchange of fire and rocket-propelled grenades, coinciding with a demonstration by Hezbollah and Amal supporters against the judicial investigator in the Beirut port explosion case.

The escalation threatens to plunge the country into a new crisis.