Lebanon's official news agency says a car bomb has exploded at a stronghold of the Shiite militant Hezbollah group in the country's east, causing a number of casualties.

The National News Agency says say the bomb went off early on Tuesday near the remote village of Sbouba in the Baalbek region.

A Lebanese security official confirmed the explosion but said there was no immediate word on the nature of the target or casualties. He spoke on condition of anonymity in line with regulations.

There has been a wave of attacks recently on Hezbollah strongholds and interests in Lebanon. The group is fighting in Syria alongside President Bashar Assad's troops and has received threats of retaliation from the largely Sunni rebels fighting to topple him.