Opposition groups, led by al-Wefaq, have repeatedly called for all protest to be peaceful.

BBC: Dozens injured as violence flares in Bahrain

The main opposition society in Bahrain , Al Wefaq, has called for a major protest on Friday, reports the BBC's Bill Law.

BBC: Fresh Bahrain clashes ahead of Formula 1 race

Earlier this year the leader of Bahrain's main opposition group, al-Wefaq, called for the crown prince to attend talks aimed at ending the unrest.

BBC: Bahrain Crown Prince Salman addresses civil rights