The town in the Bekaa Valley on Lebanon's border with Syria, is considered a Hezbollah stronghold. The blast occurred in the Sabreh Hamadeh Square in central Hermel, the Lebanese newspaper the Daily Star reported.
Marwan Charbel, the country's interior minister, told the newspaper preliminary findings indicate a suicide bomber may have been involved in the attack and four of the injured are in critical condition. He said the blast occurred about 9 a.m. and residential buildings as well as banks and shops were damaged.
Thursday's explosion occurred the same day the international court in The Hague, Netherlands, began the trial of four members of Hezbollah in absentia. They are accused of the assassination of former Lebanese Prime Minister Rafik Hariri, killed in Beirut in 2005.
Earlier this month a suicide car bomb exploded in a Hezbollah stronghold in Beirut. In December a car bomb exploded near a Hezbollah post in northeast Lebanon and in November two suicide bombers staged an attack outside the Iranian embassy in Beirut.