He says the seizure of the buildings happened on Thursday after militants from Ansar al-Sharia had warned the station to stop broadcasting music.
The group, considered a terrorist organization by the United States, is accused of being involved in a deadly 2012 attack on a US mission and annex in Benghazi. Its branch in the city of Derna has pledged allegiance to the Islamic State group.
The official said residents went about their business after the seizure and traffic flowed normally. A resident said that the radio station had begun playing religious songs and lessons. Both spoke on condition of anonymity for fear of reprisals.