The current holder of the EU Presidency, Austria, has demanded the immediate release of Alexander Kozulin, the opposition leader who was arrested in during protests in Belarus yesterday.
The statement, issued in Vienna, expressed serious concern the politician's detention.
Mr Kozulin was leading several hundred opposition supporters on a march to the main detention centre in the capital Minsk where it is thought hundreds of student demonstrators are being held.
The Belarus Interior Minister said Mr Kozulin was detained because he had called on people to attack the state.
Demonstrations have continued in recent days over the victory of President Alexander Lukashenko in a disputed 19 March poll.