Al-Wefaq, Bahrain's main opposition bloc, has said that a man has been found dead after clashes with riot police in the village of Shakhoura, a day before the Gulf state stages its Formula One Grand Prix.
Al-Wefaq named the dead demonstrator on Saturday as Salah Abbas Habib, 37, and said his body was found on the roof of a building.
It said Habib was part of a group who were beaten by police during clashes late on Friday night.
Mohammed Eissa, Habib’s brother in law, told the Reuters news agency that police had not allowed the family to see the body when they went to the compound where it was found.
"We wanted to see it before it was taken so we can identify the body, but we were told to go the morgue and identify it there," Eissa said.
In a statement on the microblogging website Twitter, the interior ministry confirmed the death and said authorities have launched an investigation into the incident.
The death came as the royal family pledged once again that the F1 event wold go ahead despite the ongoing protests by the country's mainly Shia population demanding greater rights.
"I genuinely believe this race is a force for good, it unites many people from many different religious backgrounds, sects and ethnicities," Crown Prince Salman bin Hamad Al Khalifa, who owns the rights to the event, said on Friday.
Dozens of armoured vehicles and security forces in riot gear have been deployed along the road to the Bahrain International Circuit and around the capital, Manama.
Activists said barbed wire has been installed near some parts of the main highway.
Bahraini police fired teargas to break up a protest in an area outside Manama on Saturday and protesters responded with petrol bombs.
"Protesters were at a roundabout in Diraz and police tried to move them by firing teargas. They started throwing petrol bombs back at them," a witness told Reuters.
He said there were up to 150 protesters, who had taken part in a march of several thousand people earlier for democratic reforms and against the staging of the Formula One race, and around 50 riot police in jeeps.
In another demonstration west of Manama earlier on Saturday, protesters carried banners depicting Formula One race drivers as riot police beat up protesters, activists said.
Violence has escalated in the run-up to the Grand Prix, which has come under huge criticism from country’s mainly Shia protesters, while the government wants the race to run as per schedule to send out a signal to the world of a return of normalcy.
"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."
The protesters have blamed 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.
The rulers have depicted the race - expected to draw a worldwide TV audience of about 100 million in 187 countries - as an event that will put the divided society on the path of reconciliation.
On Friday, thousands of anti-government protesters were dispersed after flooding a major highway demanding a halt to the race on the first day of practice.
Al Jazeera's special correspondent in Manama, who cannot be named for security reasons, said: "I would say about 3,000 people gathered with banners and chanting for freedom and democracy and dignity."
"That demonstration has now been effectively disrupted by the police."
He said a "good deal" of the protesters had taken cover from the tear gas and riot police in a shopping mall.
Activists said that more than 100 protest organisers were arrested this week. Police acknowledged arresting some people.