Bahrain protester's family: 'we were not allowed to see the body' Reuters

An investigation has been launched in Bahrain after an anti-government protester was found dead following clashes with riot police on the eve of the controversial Formula One grand prix.

Bahraini authorities confirmed on Saturday that the dead man was Salah Abbas Habib. It said in a statement that the 36-year-old had suffered a wound to his left side and the case was being treated as a homicide.

The public security chief, Major General Tariq al-Hassan, said: ""We are pressing ahead with our investigations with every resource available. I would ask that people await the results of the autopsy and further updates rather than relying on speculation, including rumours spread through social media. The government condemns all acts of violence and will ensure the perpetrators of this crime, whoever they may be, will be brought to justice."

The opposition group al-Wefaq said Habib's body was found on the roof of a building after he and other protesters were beaten by riot police who suppressed a demonstration in the village of Shakhura late on Friday night. They released a photograph of Habib's blood-covered body on a corrugated iron roof. He was apparently found wearing a teargas mask. Reports suggested he had been shot.

Activists raised concerns about an image of Habib's body shown on Bahraini television, which allegedly showed alterations to the crime scene.

News of his death spread quickly on Twitter amid reports of intensified security in Shakhura.

Twitter user @ToulaVlahouCBS wrote: "Bahrain says police investigating death of man, opposition claims was killed by riot police during clashes Friday", while @NABEELRAJAB said: "Martyr Salah Habib Abbas was shot and killed last night as the #Bahrain regime try to clear the way for the #Formula1 #GP".

Another claimed Salah had been a political prisoner in the 1990s, while others posted pictures of the man they believe to have been killed with a Bahraini flag around his head.

At a press conference just before the qualifying rounds of the race, opposition figures accused the regime of using indiscriminate violence against villages where there were no foreign witnesses, such as motor racing fans and journalists.

Khalil Marzooq, one of 18 al-Wefaq MPs to stand down during the suppression of last year's anti-government protests, expressed scepticism over the ability of officials to investigate Habib's death – accusing Bahrain of a chronic lack of independence in police inquiries.

He said the country's security forces was allowing gangs of pro-regime "thugs" armed with iron bars and nail-loaded sticks to operate with impunity.

He said Habib was one of the leading peaceful protesters.

"After some clashes – attack would be a better word – on Shakhura he disappeared," he said. "Then they found his body. Some witnesses from the area pinpointed where his body was. The problem in Bahrain is that we don't have a single independent body to investigate."

Several thousand anti-government protesters gathered in the city on Saturday and protesters threw petrol bombs at security officials before being dispersed by police firing tear gas. Anti-grand prix graffiti was also daubed on walls.

Dozens of armoured vehicles have been deployed on the main road leading to the Bahrain International circuit in Sakhir and in the capital, Manama, after protesters promised "days of rage" against the Formula One event. Activists say barbed wire has been installed near some parts of the road.

The race has caused anger among the mostly Shia Muslim community, who are protesting against the Sunni ruling elite and demanding democratic reform. Protesters have accused the Bahraini government of using the event to deflect attention from democracy issues in the country, and they have vowed to use it to highlight their cause.

"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."

Race organisers have refused calls to cancel the event and Bahrain's crown prince, Salman bin Hamad al-Khalifa, called it "a force for good". He warned that cancelling it would "empower extremists". Formula One chief Bernie Ecclestone has said security fears are nonsense.

Opposition leaders said about 95 protest organisers had been arrested in night raids over the past week and about 50 people have died since the unrest began in February.

In London on Saturday around 20 people staged a demonstration against the grand prix outside the Formula One office in Knightsbridge.

The human rights activist Peter Tatchell, who attended the protest organised by the campaign group Justice for Bahrain, said:

"There can be no normal sporting relations with an abnormal regime that is killing its own people."

Last year's Bahrain Grand Prix was cancelled in the wake of the unprecedented protests that followed the Pearl Revolution, the Sunni-led monarchy's short-lived experience of the Arab Spring, at an estimated cost of up to $800m (£500m).

Heavy security is in place for this year's race, with troops deployed around the circuit, 25 miles from Manama, and across the capital.