At least six people have been killed and 32 others injured by gunfire in the Lebanese capital, Beirut.
It began during a protest by the Shia Muslim groups Hezbollah and Amal against the judge investigating last year’s huge blast at the city’s port.
They said Christian snipers from the Lebanese Forces (LF) faction fired at the crowd to drag Lebanon into strife – a claim denied by the LF.
Huge tension surrounds the probe into the port explosion that killed 219.
Hezbollah and its allies claim the judge is biased, but the victims’ families support his work.
No-one has yet been held accountable for the August 2020 disaster, in which swathes of the city were devastated.
In response to Thursday’s shooting, some of Lebanon’s worst violence in years, Prime Minister Najib Mikati announced a day of mourning on Friday.
Meanwhile, President Michel Aoun said: “We will not allow anyone to take the country hostage to their own interests.”
What began as a protest outside the Palace of Justice – the main court building – by hundreds of people arguing the investigation had become politicised and demanding the removal of Judge Tarek Bitar escalated remarkably quickly, reports the BBC’s Anna Foster in Beirut.
Heavy gunfire erupted in the streets as the crowd passed through a roundabout in the central Tayouneh-Badaro area.