Bahrain was under tight security on Saturday after violent clashes between police and anti-government protesters overshadowed this weekend's Formula One Grand Prix race meeting in the Gulf state.

The protesters, mostly from the majority Shi'ite Muslim community, blame the Sunni ruling elite for shutting them out of opportunities, jobs and housing, and are keenly aware of the attention the motor race has focused on Bahrain, which in 2004 became the first country in the region to host Formula One.

Organisers have rejected calls from human rights groups to cancel Sunday's race because of what activists see as continuing political repression. The cars take to the track again on Saturday for practice and qualifying sessions.

"They need to fix the country first, then they can start looking at Formula One and other events," said Umm Hussein, one of 10,000 demonstrators who gathered near the capital, Manama, on Friday.

Police used teargas against masked youths throwing petrol bombs, who were trying to reach a traffic roundabout that was a rallying point during an uprising last year inspired by the Arab Spring revolts that toppled the presidents of Tunisia and Egypt.

Last year's race was delayed, and then cancelled, after a brutal crackdown against pro-democracy protesters in Bahrain, a financial hub and modest oil producer that is also host to the Fifth Fleet, the U.S. Navy's main outpost in the region.

Security forces from neighbouring Saudi Arabia came in, the streets were cleared and 35 people, including security personnel, died.

Since then, amid simmering unrest, Bahrain has invited in an independent commission to prescribe reforms and has enacted some, but human rights groups say there is still more work to be done. They say the kingdom's rulers are using the motor race to improve their international image.

"We are committed to our programme of reforms, but this week's unbalanced coverage does little to help the progress we are already making," a Bahrain Information Affairs Authority official said in a statement.

While sports journalists poured in to cover the race, non-sports reporters from Reuters and some other news organisations have not been granted visas to visit the Gulf island.

Hackers brought down the F1 website intermittently on Friday and defaced another site, f1-racers.net, to support what they described as the Bahraini people's struggle against oppression.

GREEN LIGHT

Manama is under tight security, with dozens of armoured vehicles stationed around the capital and the road to the Bahrain International Circuit in Sakhir. Activists say barbed wire has been installed near some parts of the main highway.

Two of the 12 teams were left rattled after witnessing protesters throwing petrol bombs. Two members of the Force India team went home to Britain although the other team, Sauber, continued with race preparations.

At Bahrain International Circuit, which has been blanketed by multiple layers of tight security, there were no incidents during Friday's practice runs.

Formula One chief Bernie Ecclestone described general security fears as 'nonsense'.

Team principals echoed the sentiment, saying they were confident in security measures, which they said were similar to arrangements seen at other Formula One races across the globe.

Of particular concern to security personnel are young Bahraini protesters carrying petrol bombs who clash with police in Shi'ite villages surrounding the capital nearly every night.

Opposition leaders say around 95 protest organisers have been arrested in night raids in the past week and 54 people wounded in clashes, in which police have fired birdshot.