The European Union's internal affairs chief warned Hungary on Thursday that its decision to ease visa restrictions for Russians and Belarusians posed a potential security threat and said she would take action if her concerns were not addressed. Hungary last month extended its "national card" immigration programme to include Russians and Belarusians, among others. The holder of such a card is allowed to work in Hungary without security clearance and can bring their families to the country. The move sparked alarm among EU officials, who said Russia and its ally Belarus could exploit the scheme to send saboteurs and spies...