Clashes broke out overnight between hunderds of anti-government protesters and police, witnesses have told the AFP news agency.

Police fired tear gas and stun grenades at protesters, who responded by hurling rocks and fire bombs while chanting "Down with [Bahraini King] Hamad [al-Khalifa]". 

Demonstrators were also calling for the release of prominent activist Abdul Hadi al-Khawaja.

In a message posted on micro-blogging website Twitter, Bahrain's interior ministry said on Sunday that Khawaja was in "good health" and would meet Denmark's ambassador today." Khawaja is a dual citizen of Bahrain and Denmark.

The Saakhir Formula 1 track, meanwhile, remains under lockdown, witnesses said, though some said that roads leading to the track had been briefly blocked by protesters who burned tyres and garbage.

Police had beefed up security around Shia villages late on Saturday in order to control planned protests. 

They also prevented planned protests at a central market, residents and witnesses said.