Bahraini police Friday clashed with opposition supporters attempting to hold what authorities said was an illegal rally in the capital, dpa reported.
Several protesters were injured as police fired tear gas and sound grenades to disperse the rally in Manama.
Police also arrested activists, including an official in the main opposition Shiite group Al-Wefaq.
The clashes come ahead of the second anniversary of the pro-reform uprising which erupted in the small Gulf kingdom in February 2011.
Bahrain's Shiite majority has since been protesting to demand political reform and greater freedoms from the Sunni monarchy.