The N.B.A. said it had worked with the State Department to ensure Kanter’s release in Romania.

As to the status of his passport, and why he was allowed to travel to London without a valid one, no official announcements have been made. But in an interview with The Oklahoman, Hadis Fetic, an executive assistant for Kanter, said that the Turkish government has been known to report citizens’ passports as stolen or missing in order to have them confiscated in foreign countries and that Fetic believes that is what happened with Kanter’s passport.

The detention occurred while Kanter, who turned 25 on Saturday, was in the midst of a tour for his Enes Kanter Light Foundation.

“The reason behind it is, of course, my political views,” Kanter said in the video.

“You guys know him by, you know, he has attacked the people in Washington,” Kanter said, referring to a recent episode involving Erdogan’s bodyguards and protesters in Washington. “He is a bad, bad man; he is a dictator, and he is the Hitler of our century.”

Kanter is known to support Fethullah Gulen, an Islamic cleric based in the United States whom Erdogan has accused of orchestrating last year’s failed coup attempt in Turkey.

If Kanter had been deported to Turkey on Saturday rather than being allowed to continue his travels, he could have faced serious difficulties. Since the failed coup, the Turkish authorities have arrested thousands of people thought to be supporters of Gulen.

Along with the video, Kanter posted two photos of himself with officers holding him at the Bucharest airport. In English, he just wrote “#FreeEnes”; in Turkish, he wrote: “Haha, the police officers guarding us are taking pictures. Who do you think you are messing with you cowards.”