Alek Sigley, the 29-year-old Australian who was missing in North Korea for more than a week, has left the country and arrived safely in China.

An upbeat Sigley briefly spoke to a throng of reporters waiting for him at the airport in Beijing on Thursday, saying: “I’m OK, I’m OK, yeah. I’m good. I’m very good.”.

Speaking in Perth, his father, Gary Sigley, said the family were “over the moon” that his son was safe, saying he understood his son had been “in constant good spirits and well the whole time”.

Australia’s foreign minister, Marise Payne, said Sigley’s release would not have happened without the help of Sweden.

Sigley’s detention was confirmed overnight by the Swedish envoy to North Korea, Payne told 2GB radio.

On Thursday morning the Swedish ambassador told Australia’s Seoul diplomatic post there was a “strong possibility that Alek may be able to be handed over to their Swedish delegation at the airport as they were leaving the DPRK [North Korea]”.

“The timeline was very tight and very short, and without the support and help of our counterparts in the Swedish government this would not have been possible, so we are deeply deeply grateful to them,” Payne said.

The Australian prime minister, Scott Morrison, had given the first public confirmation that Sigley was safe, telling parliament on Thursday afternoon that the 29-year-old had been released from detention by the repressive regime and had arrived safely in China.

“Swedish authorities advised they met with senior officials with the DPRK [North Korea] and raised the issue of Alex’s disappearance,” Morrison said.

Alek Sigley, feared detained in North Korea, now “safe and sound” in China #NorthKorea https://t.co/Kth5trPf0z — NK NEWS (@nknewsorg) July 4, 2019

“We were advised that the DPRK have released him from detention and he has safely left the country and I can confirm that he has arrived safely.

“On behalf of the Australian government I would like to extend my deepest gratitude to the Swedish authorities for their invaluable assistance in securing Alek’s prompt release, which demonstrates the value of discreet behind-the-scenes work by officials

in solving sensitive consular cases in close partnership with other governments.

“I’m sure we all could not be more pleased. We now know where he is [and] we know he is safe.”

Sigley’s father told reporters outside his home in Perth he was “over the moon” to hear his son was safe.

“On behalf of Alek’s family we are extremely pleased that Alek now is safe and sound in Beijing,” Gary Sigley said. “I’m sure he will reunited with his wife very soon and we hope to see him in the not-too-distant future as well and give him a big hug and kiss.

“We’re over the moon that he’s safe and sound and I’m sure in the coming days [and] weeks there will be more information about what has transpired.

“Of course the last week has been a very difficult week for Alek’s immediate family. We were very worried we didn’t have any news about his situation [so] we’re just so happy that situation has been resolved and we know he’s safe and sound in Beijing.”

He said he had missed a call from his son while he was shopping and had not yet been able to speak to him, but that he understood he had been “in constant good spirits and well the whole time”.

Sigley was expected to travel to Tokyo, where his wife Yuka Morinaga lives, later on Thursday.

The Swedish special envoy arrived in Pyongyang earlier this week. Payne said on Wednesday that Australia had asked the envoy to raise Sigley’s case with the North Korean government.

Kent Rolf Magnus Harstedt, special envoy of the Swedish government, and his party arrived in Pyongyang on Monday. pic.twitter.com/OjDdMzAq3F — DPRK (North Korea) 🇰🇵 (@NorthKoreaDPRK) July 4, 2019

Sigley had been studying for a master’s degree in Korean literature at Kim Il Sung university, and runs a tour company that organises trips for foreign students. He first traveled there in 2014.

He was believed to be the only Australian living in North Korea.

In March, Sigley wrote for Guardian Australia about his experience living there, saying that as a long-term foreign resident on a student visa he had “nearly unprecedented access to Pyongyang”.

“I’m free to wander around the city, without anyone accompanying me,” he said. “Interaction with locals can be limited at times, but I can shop and dine almost anywhere I want.”

It remains unclear why Sigley was detained. Richard Broinowski, a former Australian diplomat to South Korea, told ABC radio he did not think Sigley had been doing anything that would “raise North Korean suspicions”.

“I’d be very doubtful he had anything to do with espionage,” Broinowski said. His detention might have been related to the summit between Donald Trump and the North Korean leader Kim Jong-un last week, but that was also unlikely, Broinowski said.

He said Australia should reopen a diplomatic posting in North Korea.

“I think it’s always a good thing to have diplomatic accreditation in the country that you want to influence,” he said.