Violence marred Bahrain's controversial Grand Prix race as a fire bomb exploded near Force India team members and protesters clashed with police in the lead-up to the Formula One practice runs set to begin on Friday.
Security has been beefed up ahead of Sunday's race, but the incident prompted F1 officials to reassure participants that, despite the violence, Bahrain was safe.
Speaking to reporters at the Sakhir circuit, chairman of the Formula One Grand Prix Drivers Association, Pedro de la Rosa, said safety is "not a concern."
He added that he had full faith in the decision by the International Motoring Federation to hold the event despite mounting tensions in the kingdom.
Four members of the Force India team were stuck in traffic when a fire bomb exploded as they returned from the Sakhir circuit to their hotel late on Wednesday, Bahrain International Circuit chairman Zayed Alzayani told Autosport magazine.
The four mechanics apparently got caught up in a clash between protesters and police on the motorway from the capital Manama to Sakhir.
Nobody was injured.
A spokesman for the Force India team confirmed the incident and said one team member, not involved in the incident, and a contractor hired by the team, had chosen to return home as a result of the blast.
Alzayani played down the incident and said he would not request any tighter security as a result.
"It was an isolated incident ... The protesters were not targeting the cars, they just happened to be there," he said.
Force India driver German Nico Hulkenberg said it was "not right" that members of his team had been close to an exploding fire bomb, but added that he still felt safe.
Mohammad Mascati, head of the Bahrain Youth Society for Human Rights, told AFP that security forces fired tear gas and sound bombs to disperse dozens who protested in Manama on Thursday, adding that police set up checkpoints at the entrances to the capital.
In other developments, Bahrain has denied visas to foreign journalists and photographers, including from AFP, to cover the race.
An AFP photographer, accredited by the sport's governing body, the FIA (Federation Internationale de l'Automobile), was informed by Bahrain's information affairs authority that there has been a "delay to your visa application, so it might not be processed."
Associated Press said two of its Dubai-based journalists were prevented from covering the Grant Prix because they could not receive entry visas, despite also being accredited by the FIA.
Meanwhile, cameramen already in Bahrain were required to keep fluorescent orange stickers on their cameras so that they would be easily recognisable to ensure they do not cover any off-track events, such as ongoing protests.
Bahrain's main opposition group, Al-Wefaq, has called for a week of daily protests to coincide with the Grand Prix, using the sports event to focus media attention on their longstanding demands for greater equality and representation in the Sunni-ruled kingdom.
"There is a desire to take advantage of the presence of (international) press, normally barred from entering the country," said Bahraini rights activist Nabil Rajab.
"The Formula One... is a symbol of the regime, it represents its repression," said Rajab, noting that the Bahrain race was a personal project of the crown prince.
The government on Thursday barred Al-Wefaq from holding a protest in central Manama, an interior ministry statement said.
The announcement came in the wake of several demonstrations in Bahrain's Shiite villages late on Wednesday, in which police and protesters clashed.
Witnesses said police used tear gas and buckshot to disperse the crowds, wounding a number of people, with protesters hurling petrol bombs in response.
The violent clashes followed calls by the February 14 Youth Movement on social networking sites for "three days of rage" to coincide with the event.
Earlier this week, hundreds of protesters marched carrying banners calling for a boycott and a demonstration was held near Bahrain's international airport as the teams began arriving, despite the arrest of about 80 leading democracy activists.
The Bahrain Grand Prix was cancelled last year in the wake of a Shiite-led uprising against the Sunni monarchy and the brutal government crackdown that followed in which a government commission said 35 people were killed.