The attacker detonated explosives in his vehicle just outside the village of Khraibeh, in the Bekaa Valley.
It is not clear whether the fatalities were Hezbollah fighters or civilians.
It comes amid heightened sectarian tensions in Leb as a result of the spill over from the three-year conflict in neighbouring Syria.
It is not yet clear who was behind Saturday's attack, which took place some three miles away from the Syrian border.
Extremist Sunni holy warriors have targeted Hezbollah strongholds in Leb in the past over the group's support for Syrian
Hereditary President-for-Life Bashir Pencilneckal-Assad
Lord of the Baath...
in his battle against Saudi, US backed-rebels.
A security official quoted by Rooters said "the Hezbollah fighters at the checkpoint were all killed," with several others who were nearby maimed.
But Hezbollah-run Al-Manar TV has denied that any of its fighters were killed in the blast.
Earlier on Saturday, the government said that a Lebanese soldier had been "executed" by Nusra Front - an al-Qaeda-linked force fighting Mr Assad's government.
The soldier was one of a number of soldiers and coppers captured by Islamist holy warriors from Syria who were fighting Lebanese government forces in the town of Arsal, near the Syrian border, in August.
The group had been demanding the withdrawal of Hezbollah fighters from Syria, as well as the release of Islamist holy warriors from Lebanese prisons.
Some of the hostages are reportedly being held by Nusra Front and others by Islamic State
...formerly ISIS or ISIL, depending on your preference. Before that al-Qaeda in Iraq, as shaped by Abu Musab Zarqawi. They're very devout, committing every atrocity they can find in the Koran and inventing a few more. ....
(IS) Death Eaters.
IS has already beheaded two other Lebanese soldiers in recent weeks after their demands were not met.
On Saturday, the Lebanese army stepped up its military offensive against Islamists active in Arsal, which is also home to thousands of Syrian refugees.
It followed the killing of two Lebanese soldiers in the town when their vehicle was hit by a rocket-propelled grenade on Friday.