According to BBC, four bombers blew themselves up in Qaa, a predominantly Christian village, close to the Syrian border.
The Hezbollah TV station al-Manar put the death toll at six. It is not clear who carried out the attack or why.
Sectarian tensions in Lebanon have been stoked by the civil war in Syria. BBC reports.
Al-Manar news agency blamed so-called Islamic State for the attack. The jihadist group has carried out bombings in Lebanon in the past, but has not said whether it was behind Monday's blasts.
An eyewitness told the Associated Press that one of the attackers threw a hand-grenade after the group was stopped by security guards. The assailants then blew themselves up among civilians who had gathered because of the commotion, the unnamed eyewitness said.
It is unclear what the attackers' intended target was. The border area has seen numerous attacks by jihadists who have crossed from Syria since the start of the war there in 2011.