Jan Srb, spokesman of the Office for the Documentation and Investigation of the Crimes of Communism (UDV), told the Czech news agency CTK that the United States was interested in the doctors' activities during the 1950-1953 Korean War.

The UDV investigation however has not confirmed any accusations, Srb said.

In 1992, former general Jan Sejna claimed in the United States that doctors from what was then Czechoslovakia took part in experiments performed on the US PoWs.

Sejna emigrated in 1968 and worked for US intelligence.

Srb said the office was also helping uncover information about US soldiers lost during military conflicts.

After World War Two there were about 200 US soldier graves in what is now the Czech Republic and formerly was part of Czechoslovakia.

The UDV also uncovered information about 21 US military personnel arrested in Czechoslovakia during the 1950s under communism, most of whom were based in Germany and were lost on the border.

In return, the UDV is seeking help from US authorities in the case of Pavel Minarik, a Czechoslovak communist secret agent who was convicted of planning in the 1970s to bomb US-funded broadcaster Radio Free Europe in Munich, where he worked as a reporter.

The UDV asked US officials to assess the damage such an attack would have caused, to help file charges against him.

Minarik was convicted in 1993 of planning an attack and sentenced to four years in prison. After an appeal a court ordered further investigation by the UDV and the prosecution was halted last year.

The Czech Supreme Court then allowed the prosecution to continue and Minarik faces eight to 15 years in prison.

Radio Free Europe later moved its headquarters from Munich to Prague.

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