A car exploded near a Hezbollah checkpoint in eastern Lebanon early on Tuesday, causing both deaths and injuries, a security source told AFP on condition of anonymity.
Fighters of the Shiite militant group, which controls much of the Bekaa Valley region on the border with Syria, opened fire on a suspect vehicle at the roadblock, Lebanon's NNA news agency reported.
It was not immediately clear whether the driver was a suicide bomber or the small arms fire had triggered the explosion, the news agency added.
"A blast went off at around 4:00 am (0200 GMT)... near a Hezbollah position in Sbouba... causing deaths and injuries," the security source told AFP.
An AFP photographer saw four burned out vehicles at the checkpoint, one of many manned by Hezbollah in the Bekaa, which hosts tens of thousands of Syrian refugees, who now account for a fifth of Lebanon's resident population.
Hezbollah militiamen had already intercepted two car bombs earlier on the same road, NNA reported.
The Shiite militant group has been the target of repeated attack by suspected Sunni hardliners since its leader Hassan Nasrallah publicly confirmed in April that its fighters were engaged in the Syrian conflict alongside forces of President Bashar al-Assad against mainly Sunni rebels.
In recent months, several blasts have struck Hezbollah targets in both the Bekaa and Beirut.
On November 19, two suicide bombers targeted the Iranian embassy in a Hezbollah stronghold in south Beirut, killing 23 people.