Manama: Bahraini police fired teargas to break up a protest outside Manama yesterday during Bahrain's Formula One Grand Prix, and protesters responded with petrol bombs.

Earlier in the day, a man was found dead at the site of overnight clashes with police. A statement by the Interior Ministry said a probe was under way, but it gave no other immediate details.

"Protesters were at a roundabout in Diraz and police tried to move them by firing teargas. They started throwing petrol bombs back at them," a Reuters witness said.

He said there were up to 150 protesters, who had taken part in a march of several thousand earlier for democratic reforms and against Formula One, who had squared off with around 50 riot policemen in vehicles.

Demonstrators west of Manama took to the streets earlier in a march called by opposition parties, holding banners calling for democratic reforms.

In Washington on Friday, State Department spokeswoman Victoria Nuland expressed the Obama administration's concern about "the increase in violence" in Bahrain. "These are unproductive, unhelpful acts in building the kind of meaningful trust and reconciliation that is needed in Bahrain," she told reporters.