Thousands of pro-democracy demonstrators have clashed with police in Bahrain after taking to the streets in the capital Manama ahead of Sunday's Formula One grand prix.
Police fired tear gas into the crowds of protestors, some of whom were attempting to reach the heavily-guarded Pearl Roundabout, the focal point for activists last year when the initial demonstrations began.
Reports from the kingdom claimed that the police fired tear gas and sound bombs after coming under attack from petrol bombs thrown by protestors, who had taken advantage of the grand weekend to highlight their cause.
There is tight security around Manama, with armoured vehicles stationed around the capital and on the road to the Bahrain International Circuit in Sakhir where the grand prix is being held, Reuters reports. Activists have called for "three days of rage".
Earlier in the day, the Crown Prince of Bahrain insisted the race would go ahead and claimed it was a "force for good" and a way of "celebrating our nation".
Speaking to journalists during Friday's practice sessions at the Sakhir circuit, Salman bin Hamad Al Khalifa said cancelling the race would play into extemists' hands when he was more concerned about "building bridges".
"I think cancelling the race just empowers extremists," the Crown Prince said.
"For those of us who are trying to navigate a way out of this political problem, having the race allows us to build bridges across communities and get people working together."
The Crown Prince also stressed how important the race was to his country in economic terms.
"Political parties across the spectrum have welcomed the race. As far as I understand, it was a few politicians who made those comments, and it doesn't represent the entire British spectrum."
The Crown Prince was accompanied in the circuit paddock by F1's ringmaster, Bernie Ecclestone, who stressed he had no power to call off the race, and suggested if was none of his business anyway.
"It's nothing to do with us," he told a scrum of reporters. "I can't call this race off. We've an agreement to be here, and we're here.".
However, Ecclestone did question the wisdom of holding the GP, suggesting to reporters it might have not have been such a good idea: "His Royal Highness was a little bit silly putting the race on, he's given the protestors an incredible platform to talk to all you guys."
Ecclestone also scoffed at the idea that the Bahrain government was using the race for political purposes and encouraged reporters to report on more pressing issues in other countries.
"Go to Syria and write about those things there because it's more important than here," the 81-year-old said.
The Crown Prince's and Ecclestone's comments were made after it became clear that some western journalists were being refused visas to enter Bahrain. The Crown Prince did not deny that had happened but said it was not his responsbility.
"You'd have to ask the government on that point," he told the media, adding: "Personally, I feel that anyone who wants to come to the country should come."
Earlier in the day, David Cameron refused to add his voice to calls from other leading British politicians for the race to be cancelled, insisting it is a "matter for Formula One".
Speaking on a visit to Lancashire on Friday, the prime minister said it was "important that peaceful protests are allowed to go on" but added that "Bahrain is not Syria" and that there is a "process of reform" under way in the kingdom.
"This government backs that reform and wants to help promote that reform."