Sergei Tikhanovsky, the husband of Belarus' opposition leader, has called on US President Donald Trump to "just say the word" and ask for all political prisoners in Belarus to be released.

U.S. special envoy Keith Kellogg met Belarusian President Alexander Lukashenko in Minsk, the highest-profile visit of a U.S. official to the authoritarian state in years.

Belarus has freed Siarhei Tsikhanouski, a key dissident figure and the husband of exiled opposition leader Sviatlana Tsikhanouskaya, following a rare visit by a senior U.S. official.