The European Union's Ambassador to China said on Wednesday he expects Chinese authorities to immediately release Swedish citizen and Hong Kong-based bookseller Gui Minhai, echoing demands from Stockholm.

Sweden confirmed on Tuesday that Gui, who has published books on the personal lives of Chinese Communist Party leaders, was taken into custody at the weekend while traveling with Swedish diplomats to seek medical treatment in Beijing.

EU Ambassador to China Hans Dietmar Schweisgut told reporters at a briefing that the EU "fully supports" Sweden's efforts to resolve the issue with China.