HONG KONG — The former N.B.A. star Dennis Rodman has been one of the United States’ most unlikely links to North Korea, traveling repeatedly to the authoritarian state and gaining rare access to its leadership.

Now he is back, though no details have emerged of what he plans to do there. Mr. Rodman’s visit coincided with the surprise release of Otto F. Warmbier, an American college student who had been held prisoner in North Korea for more than a year. Mr. Warmbier, 23, was sentenced to a 15-year prison term for trying to steal a propaganda poster in January 2016.

Some analysts speculated that Mr. Rodman may even be carrying a message from President Trump, who had previously praised his efforts to engage North Korea.

Mr. Rodman was seen at Beijing International Airport and flew to Pyongyang, the North Korean capital, on Tuesday, CNN reported.