Bahrain has been rounding up pro-democracy activists ahead of its controversial staging of the April 21 Formula One Grand Prix two years after a bloody crackdown, Human Rights Watch said on Wednesday.
Plainclothes police officers have arrested 20 people so far in raids in towns around the Gulf state's Sakhir circuit, the New York-based watchdog said.
"Bahraini authorities are carrying out home raids and arbitrarily detaining opposition protesters in advance of the Formula 1 Grand Prix weekend," it said.
"These raids and detentions suggest that officials are more concerned with getting activists out of circulation for the Formula 1 race than with addressing the legitimate grievances that have led so many Bahrainis to take to the streets," said HRW's Middle East director Sarah Leah Whitson.
"The Bahraini authorities have a responsibility to ensure the safety of those attending the Formula 1 Grand Prix, but that should not extend to arresting people for exercising their legitimate rights to free speech and assembly.
"Night-time raids of targeted people by masked officers who show neither arrest nor search warrants appear intended to intimidate them, their families and their supporters," she said.
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Opposition groups announced Wednesday they would organise a nine-day campaign of rallies and demonstrations across Bahrain under the slogan of "Democracy is our right".
The "peaceful escalation will include a bundle of political and public activities... and an increase in protests and peaceful rallies," said the opposition, which is led by Al-Wefaq main Shiite formation.
The statement made no mention of the Formula One race as a motive for the protests which will begin on Friday.
Sunni-ruled Bahrain was rocked by month-long pro-democracy protests led by the kingdom's Shiite majority in early 2011 that were crushed with the help of Saudi-led troops.
Last year's Bahrain Grand Prix was accompanied by a week of angry Shiite-led protests but demonstrators stayed away from the desert circuit and the race passed off without incident.
A total of 80 people have been killed in Bahrain since the protests erupted in February 2011, according to the International Federation for Human Rights.