The Milwaukee Bucks are being accused by the Greek basketball federation of preventing Giannis Antetokounmpo from playing in the European championship.

About an hour after Antetokounmpo posted on Facebook and Instagram that he was unavailable because of a knee injury, the federation attacked the Bucks and the NBA in a statement, describing an "organized and well-staged plan" to keep Antetokounmpo from playing in the Eurobasket at the end of the month.

"The simultaneous report by the Milwaukee Bucks and Giannis Antetokounmpo himself, by phone and social media from faraway China, and not by the appropriate official manner, of his inability to join the national men's team saddens us ... but is not surprising," the federation said in the statement.

"A series of indications ... had convinced us of the existence of an organized and well-staged plan by (Antentokounmpo's NBA) team, with the full knowledge if not encouragement of the NBA that put the athlete on the spot and forced him to announce today that he is no longer part of the men's national team."

Takis Tsagronis, the federation general secretary, told state TV ERT that a scan revealed no problems with Antetokounmpo's knee.

"This (the player's absence) is bad but not unexpected news. All indications were that it would end up like that," Tsagronis said.

"We, on our side, did everything not to give the Bucks an excuse. We took a magnetic scan of Giannis' leg and it was clean. What the Bucks claim is not the reality; something else is happening."