(CNN) -- Opposition groups said Saturday that a protester died after clashes with security forces, amid claims the government is cracking down on demonstrations ahead of the Bahrain Grand Prix.
Bahrain's opposition party Al-Wefaq and the Bahrain Youth Society for Human Rights said the man, identified as Salah Abbas Habib Musa, took part in a peaceful protest Friday evening that was violently broken up by security forces.
His body was found early Saturday on a farm in a village outside the capital of Manama.
The interior ministry said the public prosecutor had launched an investigation into the 36-year-old man's death.
He was "pronounced dead at the scene, with a wound to his left side" and will undergo an autopsy, the interior ministry statement said. "The investigation is ongoing but the death is being treated as homicide," it said.
Police and protesters clashed in the area Friday night, witnesses told the Bahrain Youth Society for Human Rights, with security forces using of tear gas, bird shot and stun grenades. Several protesters were detained by riot police, the witnesses said.
The ministry appealed for people to await the results of the autopsy rather than heeding speculation on social media about how the man died.
"The government condemns all acts of violence and will ensure the perpetrators of this crime, whoever they may be, will be brought to justice," said public security chief Maj. Gen. Tariq al Hassan.
Bahraini Foreign Minister Sheik Khalid bin Ahmed bin Mohammed al-Khalifa spoke Saturday with British Foreign Secretary William Hague about the situation, according to Britain's Foreign and Commonwealth Office.
Hague said that he spoke to his Bahraini counterpart "to express our concern about the violence in Bahrain, to call for restraint in dealing with protests -- including during the Formula 1 race -- and to urge further progress in implementing political reforms," according to the statement.
The British government "supports the reforms already underway," including efforts to hold those "responsible for human rights abuses" accountable, and called for "the release of prisoners sentenced by the military court."
There are mounting fears that civil unrest in Bahrain could upend Sunday's race and pose a threat to Formula 1 teams and fans.
Last year's race was canceled twice because of unrest. But the sport's governing body said Friday that the 2012 event would go ahead as planned despite tension on Bahrain's streets, while Crown Prince Salman bin Hamad Al-Khalifa said a cancellation plays into extremists' hands, according to a state-run Bahrain News Agency report.
Authorities manned check points on Manama streets and near the race circuit Saturday, but the security presence is less heavy than a day earlier, witnesses say.
The Bahraini government played down any risk to visitors Friday, when preliminary race events got under way, saying the Grand Prix would act as a unifying force amid the nation's civil unrest.
"The government guarantees the safety of everyone. We are very confident about our security measures that we have in place," Fahad Albinali, spokesman for the Bahrain Information Affairs Authority, told CNN.
Former lawmaker Mattar Mattar has claimed the government increased the number of arrests in the days leading up to the event. A human rights activist, Nabeel Rajab, also accused the government of detaining and torturing "at least half" of the Formula 1 staff in Bahrain.
The crown prince, meanwhile, described demonstrations that took place Friday were part of the political process, like in any country, the Bahrain News Agency reported. That day, tens of thousands attended an anti-government protest in Manama, with many continuing to the former Pearl Roundabout -- the center of last year's revolt -- activist Mohammed Muscati told CNN.
Claiming that some security personnel who had been heavy-handed in the past have been held accountable, he condemned violence on all sides -- including by demonstrators trying to get, in his words, the world's attention.
Specifically, the government denied that any torture or mistreatment of Bahraini racing employees has occurred, adding that it takes such allegations seriously.
Bahrain has declined to extend the visas of non-sports reporting crews from CNN, Reuters and other news agencies and told them they would not be allowed to stay for the race, which is a big draw, both in terms of investment and fans.
Formula 1 is the world's most popular motor sport, and races have a TV audience of more than 500 million. When Bahrain canceled the race last year, it lost an estimated $480 million to $800 million of investment that would have come from hosting it.
The unrest in Bahrain makes hosting the race precarious, because the racers must pass through areas where clashes have occurred to get to the circuit, which is in the desert.
CNN's Fred Pleitgen, Salma Abdelaziz and Becky Anderson contributed to this report.