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The Bahrain Grand Prix may be going ahead but it will not be without controversy.

Demonstrations have been taking place in the kingdom with opposition groups calling for the race to be called off.

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Tension is building in Bahrain ahead of this weekend's Formula 1 race.

Protesters and opposition groups have been holding daily demonstrations to try and force the cancellation of the event.

The protests, dubbed by opposition groups as "the week of steadfast and challenge", have been held across the kingdom with thousands joining a protest rally march in Tubli late on Wednesday.

According to activists, that protest was peaceful but others have turned increasingly violent.

A firebomb exploded on Wednesday night in Bahrain's capital Manama, causing a Force India van with four team members to be delayed in traffic on its way from the Bahrain Grand Prix circuit back to its hotel.

No one in the vehicle was hurt and none of the four passengers were Formula One drivers, according to Force India officials.

Two members of the team decided to leave Bahrain following the incident.

The Bahrain GP was cancelled last year due to anti-government protests that left nearly 50 dead.

But last week, Formula One boss Bernie Ecclestone declared the Gulf kingdom safe and decided to go ahead with this year's race.

Protesters argue that the F1 decision to return to Bahrain gives greater international legitimacy to the monarchy and its crackdowns, which rights activists claim have included waves of arrests in the past week.

On the track, teams will be practicing on Friday and Saturday before qualifying later on Saturday.

The race is scheduled for Sunday.