Iran condemned the killing of protesters in Lebanon, describing Thursday's shootings as seditions backed by Israel, state-run Press TV said on Twitter on Friday.
"Iran believes that the people, the government, the army and the resistance in Lebanon will successfully overcome seditions backed by the Zionist entity," IRNA news agency quoted the Iranian Foreign Ministry spokesman Saeed Khatibzadeh.
Heavy gunfire broke out Thursday in Beirut during a protest organized by the Hezbollah group against the judge leading the probe into last year's blast in the city's port. At least six people were killed and dozens wounded in the most violent street fighting in the Lebanese capital in years.
It was not clear who started the shooting, which began shortly after the start of the protest organized by the Iran-backed Hezbollah and its Shiite allies from the Amal Movement against Judge Tarek Bitar, who is leading the investigation into last year's massive port explosion. Hezbollah and its allies accuse the judge of singling out politicians for questioning, most of them allied with Hezbollah.
Bitar is the second judge to lead the complicated investigation. His predecessor was removed following legal challenges.
On Thursday, shortly before the planned protest, an appeals court turned down a request to remove Bitar from his post filed by two lawmakers who are defendants in the case, both of them allies of Hezbollah.
The calls for the judge's removal upset many who considered it blatant interference in the work of the judiciary.
The Islamic Republic and Jewish state are long-time arch enemies and have been engaging in a shadow war for years with the former repeatedly calling for the latter's annihilation.
Jerusalem has been trying to thwart Tehran's nuclear program through mobilization of international pressure and alleged clandestine sabotage operations, vowing to stop it from obtaining nuclear arms. Iran rejects such claims and says its nuclear program is meant to serve peaceful purposes only.
Hezbollah and Iran are both a part of a Shiite Muslim axis that seeks, among other things, the destruction of the State of Israel. The Lebanese group — which is designated as a terrorist organization by the European Union and the United States — has fought two wars with Israel, one in 1982 which led to a subsequent 15 years of low-scale armed conflict and another in the summer of 2006.