Blast rocks Hezbollah site in south Lebanon: residents
An AFP photographer said members of the group had cordoned off the area.
Residents said ambulances had carried away several wounded, while the National News Agency reported limited material damage.
A military source said preliminary information showed the blast happened at a "Hezbollah centre containing munitions".
Footage shared on social media showed a huge plume of dark grey smoke rising from the site of the explosion.
The Shiite movement did not immediately comment on the blast.
Hezbollah, backed by Iran, is the only Lebanese non-state armed group not to have disarmed after the 1975-1990 civil war.
It has fought several wars with neighbouring Israel, Iran's arch-enemy.
The National News Agency said the blast had coincided with intensive fly-overs by Israeli fighter jets and drones.
There was no immediate statement from the Jewish state.
Lebanon is still reeling from a massive explosion of hundreds of tonnes of ammonium nitrate at Beirut's port last month that killed more than 190 people, wounded thousands and ravaged swathes of the capital.
The exact cause of that explosion is still unclear.