Explosion in Hezbollah stronghold in south Beirut

Lebanese security officials say an explosion struck a neighborhood in south Beirut.
The officials say the nature of the explosion today in the suburb of Beir el-Abed, a stronghold of the Shiite militant Hezbollah group, was not immediately clear. They spoke on condition of anonymity in line with regulations.
Two rockets hit south Beirut several weeks ago wounding a number of people.
Some Syrian rebel groups have threatened to strike in Lebanon after Hezbollah joined Syrian President Bashar Assad's troops in their battle against opposition fighters.