Prosecutors in Istanbul allege that Enes Kanter, a Turkish center for the New York Knicks, belongs to the movement of cleric Fethullah Gulen, which Turkey regards as a terrorist organization, and have sought government help to publicize an arrest warrant for Mr. Kanter through Interpol, a Turkish official said Tuesday.

The 26-year-old Mr. Kanter, who has been playing in the NBA since 2011, calls himself a “servant” of Mr. Gulen, who lives in Pennsylvania. But the basketball player denies the organization of Mr. Gulen has had any involvement in terrorism-related activity. Mr. Gulen has denied playing any role in the failed coup.

Mr. Kanter said Tuesday that he didn’t fear Mr. Erdogan. “There is god and no sadness,” he said on Twitter shortly after Istanbul prosecutors announced they were seeking his extradition.