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MOSCOW (Reuters) - A court in Moscow on Tuesday ordered eight Ukrainian sailors seized by Russia last year off the coast of Crimea to be kept in pre-trial detention until April 24, Russian news agencies reported.

Russia seized 24 men and three Ukrainian navy vessels on Nov. 25 near Russian-annexed Crimea. Moscow accuses them of illegally entering Russian waters, something Kiev denies.

The court hearings were closed to the public, but the Ukrainians were shown on state television in the custody of armed security officers in masks.

It was not immediately clear if any others among the 24 would appear in court.

The United States and European Union have called on Russia to release the men, but the Kremlin has said they must be put on trial.

No date has been set for a trial.

Moscow could hand over the men as part of a prisoner swap deal with Ukraine later this year, a Russian diplomatic source was quoted as saying last week by the pro-Kremlin Izvestia newspaper.