Lebanese Shiite and Sunni groups traded machine gun fire in Beirut on Tuesday, killing one person and wounding at least three others, security officials said.
The shootout, involving machine guns and rocket propelled grenades, erupted between the supporters of the Shiite Hezbollah and a Sunni conservative group in a mixed residential neighborhood near Beirut's downtown, they added.
The officials said the other side was the pro-Syrian, Sunni Muslim Association of Islamic Charitable Projects, known as the Al-Ahbash group, that has a history of feuding with Hezbollah.
They spoke on condition of anonymity in line with regulations.
Families were seen running for cover as the two sides traded fire amid the crash of rocket propelled grenades, while gunmen stood on corners and peered down allies.
Army troops cordoned off the area, keeping out journalists while the crackle of sniper fire could be heard.
The fighting was audible in downtown Beirut, which is packed with tourists at this time of year.
The fighting took place as Hezbollah leader Sheik Hassan Nasrallah addressed supporters, calling for increased military assistance for the Lebanese army from its Arab neighbors.
Lebanon has a history of deadly sectarian strife. Tensions have been running high in recent weeks over signs a U.N. tribunal could indict Hezbollah in the 2005 killing of former Prime Minister Rafik Hariri.
The Hezbollah leader Sheik Hassan Nasrallah has said he has information that the tribunal will implicate Hezbollah members, but he says the tribunal is an "Israeli project" and has no credibility.