Six people were reportedly wounded.
Witnesses in Jounieh, 15km (10 miles) north of Beirut, said the explosion occurred near the main square of the picturesque town. The nature of the explosion and its target were not immediately clear.
The explosion was heard in the hills overlooking the coast shortly after 9pm (1800 GMT).
The explosion was reported by LBC television, whose studios are several kilometres north of the city, and Future TV, a private station.
Both stations quoted security sources as saying six people were wounded.