Bahraini opposition protesters seeking to highlight pro-reform demands clashed with police on Friday as Formula One Grand Prix practice sessions passed unhindered by the unrest, away from the circuit.
Meanwhile, Bahrain said it was expelling journalists working for Britain's ITV television for "violating the laws and regulations" of the small, Shiite Muslim-majority Gulf kingdom ruled by a Sunni dynasty.
The measure was taken "to ensure preserving the national security of Bahrain," an Information Affairs Authority statement added.
Supporters of the radical February 14 Revolution Youth Coalition, which had called for a "Day of Rage", tried to march on the former Pearl Square in Manama, the focal point of Shiite-led pro-democracy protests in February and March 2011.
Police fired tear gas and birdshot to disperse them before they neared the area, witnesses said, but no casualties were reported.
The movement's supporters -- armed with petrol bombs and stones -- clashed with police in Shiite villages outside the capital and burnt tyres to block main roads, the sources said.
"Your race is a crime," chanted the protesters. "No, no to the blood Formula."
All of the violence was at a distance from the Sakhir race circuit, south of Manama, where practice sessions passed unaffected.
Meanwhile, thousands of supporters of the more moderate Shiite opposition bloc Al-Wefaq marched peacefully on the Budaya highway, four kilometres (2.5 miles) west of Manama, which links a string of Shiite villages with the capital.
"F1 is just a mask to hide the crimes," read their banners in English. Some waved flowers alongside Bahraini flags. "No to the illegitimate government."
Al-Wefaq had urged on its Twitter page that participants demonstrate in a "disciplined and civilised way that suits our people."
Police did not intervene.
Security forces have been on high alert during days of protests to prevent clashes from marring the race, which is seen as a booster to the image and economy of the tiny Gulf monarchy torn by Arab Spring-inspired unrest.
Checkpoints were set up at major intersections, particularly on roads leading to the F1 circuit.
World motorsport's governing body the FIA and promoters Formula One Management said the race should take place on Sunday, despite the demonstrations.
"The Federation Internationale de l'Automobile and Formula One Management wish to jointly confirm their belief that the Bahrain GP should go ahead this weekend, following assurances from the local promoter and the authorities that security, their responsibility, will be guaranteed for all participants," a statement read.
Bahrain, home to the US Navy's Fifth Fleet, was rocked by month-long protests in early 2011. They were crushed with the help of Gulf troops led by neighbouring Saudi Arabia.
Government spokeswoman Samira Rajab said "Bahrain is ready to host the F1 and there are no security issues," dismissing the protests as "childish movements implementing Iranian agendas... that will not affect the race."
Police have been rounding up pro-democracy activists in an attempt to head off protests.
Bahrain International Circuit chairman Zayed Alzayani said he hoped to fill the grandstands for the race on Sunday, insisting it was safe to go ahead with the event.
In London, ITV said a five-strong team, which had the necessary visas to work, were filming when they were detained. It said they were questioned, released and questioned again before being told they must leave the country or face prison.
"Having filed a report last night, they were stopped while filming this morning and taken to a local police station for discussions with officers," a spokeswoman said..
"They have since been asked to leave the country, which they are in the process of doing."
The event was cancelled in 2011 but went ahead last year.
Strategically situated across the Gulf from Shiite-ruled Iran, Bahrain has continued to witness sporadic demonstrations, now mostly outside the capital.
Human rights groups say a total of 80 people have been killed in the unrest in Bahrain since February 2011.