A protester was found dead on a rooftop in Bahrain Saturday after overnight clashes with police, stirring more fury on the eve of a Formula One Grand Prix that anti-government activists vow to mark with days of rage.

Bahrain's government has spent $40 million to host the global luxury sporting event, hoping to demonstrate that normal life has returned to the Gulf island kingdom after it cracked down harshly on Arab Spring demonstrations last year.

But vivid televised images of streets ablaze - as masked youths hurl petrol bombs and police fire teargas and birdshot - threaten to embarrass Formula One and the global brands that lavish it with sponsorship.

The government are using the Formula One race to serve their PR campaign, said rights activist Nabeel Rajab. It's not turning out the way they wanted.

Opposition party Wefaq published a photograph of a body splayed on a corrugated iron rooftop, identifying him as Salah Abbas Habib, 37. It said he was among a group of protesters who had been beaten by police after fierce clashes on Friday night.

More violent demonstrations were expected later on Saturday, and a funeral march for Habib will take place on Sunday, setting the stage for riots during the big race itself.

Habib's death will infuriate members of Bahrain's Shi'ite Muslim majority, who complain they have long been marginalised by the Sunni ruling family and have been treated brutally since the crackdown on protests last year.

The uprising forced the cancellation of last year's Grand Prix, but this year the authorities were determined to stage it. Organisers and sponsors have ignored calls from human rights groups for a boycott. Thomson Reuters, parent company of Reuters, sponsors the Williams Formula One team.

MORE MARCHES PLANNED

An opposition march later on Saturday is expected to match the scale of protests on Friday, when thousands took part.

The overnight battles saw police fire teargas at masked youths throwing petrol bombs, who tried to reach a traffic roundabout that was the main rallying point during last year's uprising. Hundreds of protesters took refuge from teargas in a shopping mall.

The protests have so far been kept away from the Bahrain International Circuit, where qualifying races were held on Saturday in advance of Sunday's main race.

Armoured vehicles and security forces in riot gear guarded the highway during Friday's clashes.

The protesters, mostly from the majority Shi'ite Muslim community, blame the Sunni ruling elite for shutting them out of opportunities, jobs and housing. They have made it clear they will use the international attention the motor race has focused on Bahrain to air their grievances.

According to Mohammed al-Maskati of the Bahrain Youth Society for Human Rights, three witnesses who took part with Habib in Friday night's clash said was hit by birdshot while running away from police before they lost him.

They said they don't know if he died from the birdshot or from being beaten up by security forces, Maskati said, adding police appeared to know where his body was when they went to the village of Shakhura early on Saturday morning.

Bahrain's Interior Ministry said via Twitter that it was launching an investigation into Habib's killing.

Bahrain, a financial hub and modest oil producer, is an important U.S. military ally and host to the Fifth Fleet, the U.S. Navy's main outpost in the region.

It is the only one of the Gulf's Arab monarchies with a Shi'ite majority, and the only one that was seriously threatened by last year's Arab Spring, which swept away the long-serving rulers of Tunisia, Egypt, Libya and Yemen.

During last year's crackdown, Bahrain brought in troops from neighbouring Saudi Arabia. Security forces cleared the streets and bulldozed the landmark Pearl Roundabout. Thirty-five people, including security personnel, were killed.

Since then, with protests and clashes continuing, 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 have been invited to cover the race, non-sports reporters from Reuters and some other news organisations have been denied visas.

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

At stake is a race that has drawn more than 100,000 visitors and generated more than $500 million in spending.

The pride of Bahrain's ruling royal family is also under threat. It was Crown Prince Sheikh Salman bin Hamad al-Khalifa who brought the race to the country in 2004, securing the first Formula One event in the region.

Some of the 12 teams have witnessed clashes. Two members of the Force India team went home to Britain. Force India returned to the track after skipping a practice session on Friday.

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.

Opposition leaders say over 100 protest organisers have been arrested in night raids in the past week and dozens have been wounded in clashes in which police have fired birdshot directly and live rounds into the air.

Also of concern is the health of hunger striker Abdulhadi al-Khawaja, one of 14 men jailed for leading last year's uprising. Khawaja's family said he stopped drinking water on Friday, after being on hunger strike for more than 70 days.

His death would be a major blow to the government, which is trying to make the case that reforms are under way.

His release, however, would also be a loss of face and could energise the opposition. Denmark, where Khawaja also holds citizenship, has offered to take him.

His situation is very dangerous, said activist Rajab. If he dies that will make people very angry.

Instrumental in founding found the Bahrain Centre for Human Rights, Khawaja is one of eight serving life sentences after he expressed support last year for Bahrain becoming a republic.

(Additional reporting by Warda Al-Jawahiry; Writing by Reed Stevenson and Andrew Hammond)