Bahrain's influential Shiite opposition bloc Al-Wefaq and a more radical group have called separate rallies for Friday to protest the weekend staging of the Formula One Grand Prix in Manama.
Demonstrations have been held during the three-day Grand Prix event every year since 2011 by opponents of the ruling Sunni Al-Khalifa dynasty in an attempt to highlight pro-reform demands.
The protests, which first erupted in the wake of a Shiite-led uprising in February 2011, have at times been marred by violence but the race has never been affected.
They are mainly staged in Shiite villages surrounding Manama and away from the Sakhir F1 circuit in the capital's south.
The Bahrain Grand Prix practice sessions begin on Friday ahead of Sunday's race.