At least three people have been killed in clashes in the Lebanese town of Baalbek after armed men opened fire on a checkpoint manned by the Lebanese Shia Muslim group Hezbollah, security sources say.
At least one Hezbollah member was killed and two others wounded when the assailants, believed to be from a Sunni Muslim clan residing in eastern Lebanon, opened fire from a car at the checkpoint.
Hezbollah members returned fire, killing two men and wounding three, the sources said.
The Lebanese army said in a statement that three people were killed and several others wounded in the clashes.
Hospital officials in Baalbek, in the eastern Bekaa Valley, put the death toll at five, including a vegetable vendor and another bystander.
The medical officials spoke on condition of anonymity because they were not authorised to brief the media.
By nightfall, security forces backed by tanks had deployed in the streets and set up checkpoints in an effort to restore calm, a resident said.
Saturday's incident was the second this week in the Bekaa Valley, a Hezbollah stronghold close to the border with Syria.
Hezbollah fighters traded fire with Sunni fighters at the same checkpoint on Wednesday, resulting in two passers-by and a Hezbollah member being wounded.
Several rockets have been fired at Shia-majority areas in the Bekaa Valley by suspected Syrian opposition fighters or their supporters.
Hezbollah set up checkpoints in its strongholds after a blast in Beirut's southern suburbs killed 27 people on on August 15.
Hezbollah members and Sunni fighters have travelled from Lebanon in recent months to join opposing forces in the Syrian civil war pitting mainly Sunni rebels against the government of President Bashar al-Assad, who belongs to the Alawite sect, a Shia offshoot.
Their involvement in the conflict has stirred sectarian tensions across Lebanon, which has erupted at times into street fighting, car bombings and rocket fire.