Clashes between security forces and protesters left several people wounded across Bahrain's Shiite villages ahead of its controversial Grand Prix as authorities beefed up security for the first practice sessions on Friday.

‘Eighteen people were wounded’ when security forces fired buckshot and tear gas to disperse overnight protests in Shiite villages, said the president of the Bahrain Youth Society for Human Rights, Mohammed Maskati.

Witnesses said the clashes in villages located far from the Sakhir circuit where practice sessions started at 0700 GMT for Sunday's Formula One race continued into the early morning.

"The people want to topple the regime," shouted dozens of protesters as they carried pictures of jailed hunger striker Abdulhadi al-Khawaja. ‘Down Hamad’, they called, referring to Bahrain's king.

Met by tear gas, sound bombs and buckshot, the protesters hurled petrol bombs at security forces, witnesses said. Maskati said he was a participant in a march in Bani Jamra village where tear gas was fired at activists.

The protests were "a message to those taking part in the F1 race to bring their attention to human rights violations in Bahrain," Muscati said, adding that ‘95 people have been arrested since April 14’.

The protesters burned tyres, briefly blocking several main roads leading to the Sakhir circuit, witnesses said.

They said police cars were deployed on roads between the airport and the circuit. A small armoured police vehicle was seen on the roadside at the entrance to a neighbourhood in Manama.

A fire bomb exploded late on Wednesday near Force India team members during clashes between protesters and security forces.

The incident prompted one team member, not involved in the incident, and a contractor hired by the team, to return home despite reassurances by officials that Bahrain was safe.

Speaking to reporters at the Sakhir circuit, the chairman of the Formula One Grand Prix Drivers' Association, Pedro de la Rosa, said Thursday that safety was ‘not a concern’.

He had full faith in the decision by the International Motoring Federation to hold the event despite mounting tensions in the kingdom.

Caught up in a clash between protesters and police on the motorway from Manama to Sakhir, four members of the Force India team were stuck in traffic when a fire bomb exploded as they returned from the circuit to their hotel late on Wednesday. Nobody was injured.

The February 14 Youth Movement has called on social networking sites for ‘three days of rage’ to coincide with the event.

And Bahrain's main opposition group, Al-Wefaq, called for a week of daily protests during the Grand Prix, to focus media attention on their longstanding demands for greater equality in the Sunni-ruled kingdom.

The government has barred the opposition from holding protests in Manama itself.

Earlier this week, hundreds of protesters carrying banners held a demonstration near Bahrain's international airport as the race teams flew in.

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.