PYONGYANG, North Korea -- Dennis Rodman, the former NBA bad boy who has palled around with North Korean leader Kim Jong Un, began sightseeing in Pyongyang on Wednesday during a trip he said he hoped will "open a door" for his former "Celebrity Apprentice" boss -- U.S. President Donald Trump.

Hours after his arrival, U.S. Secretary of State Rex Tillerson announced that North Korea had released an American student serving a 15-year prison term with hard labor for alleged anti-state acts. The family of Otto Warmbier said he was in a coma and was on a Medivac flight home. Tillerson said the State Department secured his release at Trump's direction, and a department spokeswoman was firm in saying Rodman's trip had nothing to do with Warmbier's release.

Rodman, one of the few people to know both of the nuclear-armed leaders, sported dark sunglasses and athletic wear as he left his hotel in a black limo Wednesday morning without comment. He is scheduled for sightseeing events and a meeting with North Korea's sports minister before he leaves the country on Saturday.

He was met by North Korean Vice Minister of Sports Son Kwang Ho at the airport, saying then, "I'm just here to see some friends and have a good time."

It was a relatively low-key arrival after his four past trips since 2013 generated a lot of publicity -- most of it unfavorable -- and did little in terms of diplomacy. His current visit has already been roundly criticized by some for its timing, during high tensions between the U.S. and North Korea over its weapons programs and recent missile launches.

"Well, I'm pretty sure he's pretty much happy with the fact that I'm over here trying to accomplish something that we both need," Rodman said in Beijing when asked if Trump was aware of the trip.

Rodman said the issue of several Americans detained by North Korea is "not my purpose right now," in remarks made in Beijing before the release of Warmbier was publicly disclosed.

The University of Virginia student from suburban Cincinnati who publicly confessed to trying to steal a propaganda banner left North Korea on Tuesday morning, a foreign ministry official confirmed.

Warmbier's parents said in a statement to The Associated Press that they had learned only a week ago that their son has been in a coma since March 2016.

Tillerson said the State Department is continuing to discuss three other detained Americans with North Korea.

In Tokyo, a visiting senior U.S. official said Rodman is making the trip as a private citizen.

"We are aware of his visit. We wish him well, but we have issued travel warnings to Americans and suggested they not travel to North Korea for their own safety," U.S. Undersecretary of State Thomas Shannon told reporters after discussing the North Korean missile threat and other issues with Japanese counterparts.

In 2014, Rodman arranged a basketball game with other former NBA players and North Koreans and regaled leader Kim with a rendition of "Happy Birthday." On the same trip, he suggested an American missionary was at fault for his own imprisonment in North Korea, remarks for which he later apologized.

Any visit to North Korea by a high-profile American is a political minefield.

Rodman has been criticized for failing to use his influence on leaders who are otherwise isolated diplomatically from the rest of the world. He has generally brushed off such criticism as unfair because, as an athlete and celebrity, he shouldn't be expected to solve difficult political problems.

Americans are regarded as enemies in North Korea because the two countries never signed a peace treaty to formally end the 1950-53 Korean War. Thousands of U.S. troops are based in South Korea, and the Demilitarized Zone between the North and South is one of the most heavily fortified borders in the world.

A statement issued in New York by a Rodman publicist said the former NBA player is in the rare position of being friends with the leaders of both North Korea and the United States. Rodman was a cast member on two seasons of Trump's TV reality show "Celebrity Apprentice."

Rodman tweeted that his trip was being sponsored by Potcoin, one of a growing number of cybercurrencies used to buy and sell marijuana in state-regulated markets.

There is an internet urban legend that North Korea is a pothead paradise and maybe even the next Amsterdam of pot tourism. But the claim that marijuana is legal in North Korea is not true -- it's considered a controlled substance in the same category as cocaine and heroin.

Americans have been sentenced to years in North Korean prisons for seemingly minor offenses and likely could not expect leniency if the country's drug laws were violated.