The clash occurred at the start of the trial of a journalist accused of insulting a senior foreign ministry official

BBC correspondent in Havana, Tom Gibb, says such disturbances are highly unusual in Cuba.

Disturbances are rare in Havana

The scuffles in which, the two sides traded insults, slogans and blows, lasted about half an hour and led to the suspension of the trial.

The trouble began as about 100 people milled around Havana's Provincial People's Court.

Sympathisers of the journalist, Mario Viera, gathered around him carrying a small Cuban flag and chanting "Mario is telling the truth!"

Tempers flared when a government supporter started yelling at them: "We Cubans are free in this country! Long live the Revolution! Down with the worms!"

Black beret special police turned up with sirens wailing and dragged away at least three anti-government protesters including a blind woman and a doctor.

But our correspondent said the police ignored the pro-government militants as they threw punches at their opponents and ripped the Cuban flag from them.

The incident was the most significant outbreak of public unrest since a rowdy demonstration outside the same courtroom after the trial and conviction of another dissident in August.

Constant harassment

Mr Viera, 59, who works for the illegal Cuba Verdad [Cuba Truth] news agency, faces a maximum one-year jail term if convicted.

He is accused of having insulted Jose Peraza Chapeau, the head of the foreign ministry's legal department, after branding him a hypocrite in an article.

Mr Chapeau had called for a truly independent International Criminal Court to be set up by the world community.

But Mr Viera said this was hypocritical because courts in Cuba were not independent.

Cuba Verdad is one of several illegal opposition agencies which publish articles largely outside the country and on the internet.

Our correspondent says they are subject to constant harassment by the authorities who keep tight control over all media outlets on the island.