Bahraini police had clashed on Sunday with demonstrators holding a sit-in at the Gulf Arab state's airport to protest against the arrest of Sanad.
Police dispersed the protesters who were demanding the release of Sanad who, an Interior Ministry official said, was detained hours earlier on security charges, Aljazeera said.
Bahrain has a history of political tension over unemployment and alleged human-right abuses.
The Gulf Arab state first witnessed political unrest in the 1980s and the 1990s by its Shia Muslim majority who were demanding more rights from the Sunni-led government.
Since coming to power in 1999, Bahrain's King Hamad bin Isa al-Khalifa has introduced some political reforms, including pardoning political prisoners and exiled activists.