Explosions at a Hezbollah weapons cache in the Bekaa valley in eastern Lebanon killed nine people on Wednesday, among them Hezbollah fighters, a security official and the Shiite militant group said.
The security official said nine people were killed and seven wounded in the blasts. He said four Syrian migrant workers were among the casualties, adding that one or more of them might have been among the dead.
Hezbollah said three of its fighters were killed in what it said was an accident at the storage depot.
"Sources from the Resistance (Hezbollah's military wing) reported that a blast took place in an arms depot of shells, ammunition and remnants of Israel's shelling in the area," the group in a statement carried by its Al-Manar television channel.
"This unfortunate blast led to the martyrdom of three fighters. Work is continuing in order to deal with the accident, in coordination with the relevant agencies," it added.
Residents said the arms depot was concealed in a building still under construction in an uninhabited area between the villages of Nabishit and Khodr close to the Syrian border.
The area is a stronghold of Hezbollah, and its militants surrounded the site of the explosion preventing journalists from approaching.
"No one knew there was an arms depot in the area," said resident Ali al-Moussawi.
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"When people heard the blast, people were frightened, especially families with children."
Hezbollah, which fought a devastating 2006 war with Israel, has a huge arsenal of tens of thousands of rockets, which it says it needs to retain in case of any new conflict with the Jewish state.
Hezbollah and its allies, which lead Lebanon's governing coalition, support Syrian President Bashar al-Assad in his 18-month battle against rebels seeking to oust him. The Lebanese opposition is bitterly opposed to the Damascus regime.
On Tuesday, a senior Hezbollah commander was buried in the Bekaa valley, the Shiite movement said, as Syrian rebels claimed he was killed in Syria.
Ali Hussein Nassif alias Abu Abbas "died while performing his jihadist duties," Hezbollah-affiliated website moqawama.org. said, without specifying how, when or where the commander was killed.
A Syrian rebel commander told AFP that Nassif was killed inside Syria by an improvised mine near the besieged rebel-held town of Qusayr.
In recent months, Hezbollah has announced several similar burials of its members, without elaborating on the circumstances of their deaths.
The Lebanese opposition and the Syrian rebels have repeatedly accused Hezbollah of sending fighters to assist Assad's regime in its deadly crackdown, a charge the militant group denies.