The fighting in Baalbek, a Hezbollah stronghold in the Bekaa Valley, began around noon at a checkpoint run by the Shiite militant group and raged throughout the afternoon.
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.
The Lebanese army said in a statement that three people were killed and several others wounded. Hospital officials in Baalbek put the death toll at five, including a vegetable vendor and another bystander.