An eighth Shiite was sentenced to three years in prison while two others, on trial over the same case, were acquitted, the source said.
The group were also accused of setting a police station ablaze in the Shiite village of Sitra using petrol bombs and of taking part in an "unauthorised gathering," according to the charge sheet.
Bahrain, a Gulf kingdom ruled by the Sunni Al-Khalifa dynasty, was rocked by Shiite-dominated demonstrations in February and March 2011.
According to the International Federation for Human Rights, around 80 people have been killed in Bahrain since the violence first broke out in 2011.