Czech police used violence bordering on torture against activists detained during riots at last year's IMF/World Bank meetings in Prague, Amnesty International said in a report.
Police detained 850 Czechs and foreigners in clashes during the September meetings and charged 19 with various crimes.
Amnesty said that police were brutal to the detained activists after they were taken to police stations.
In a few reported cases, in view of the severity of the force used by the police officers involved, and the pain and injuries which had been suffered by the victims, Amnesty International considers that the ill-treatment inflicted by police officers may amount to torture, the report said.
Many of the detainees were beaten, held in overcrowded cells and denied adequate food, water and medical care, the report said.
It also said they were not allowed to contact lawyers or consular officials, and they were not informed of their rights in a language they could understand.
The Czech Police Presidium denied the allegations.
"The police of the Czech Republic considers it essential to refute the generalised claims of ill-treatment with detainees, their harassment and even torture," it said in a statement.
Czech police and the Interior Ministry have also denied the charges and allegations that they were dawdling in investigating complaints filed by the detainees.
Activists threw gasoline bombs and cobblestones at police, who responded with water cannons, batons and teargas. The fighting left dozens on both sides injured.
Police have charged the Czech and foreign activists with violence against police and property damage.