Mr. Choi was a naturalized Australian citizen who had lived in the country for more than 30 years, the police said. They did not elaborate, but some Australian news media reports said he was born in South Korea.
“We think he’s acting as an economic agent on behalf of North Korea,” Mr. Gaughan said at a news conference. “He’s doing it out of a patriotic purpose. I think at the end of the day, he’d sell whatever he could to make money back for the North Korean government.”
The police said evidence suggested that Mr. Choi had been in “contact with high-ranking officials in North Korea” but would not comment further.
Mr. Choi was also charged with attempting to sell North Korean coal in countries such as Indonesia and Vietnam, the police said, adding that there was no evidence of involvement by those countries’ governments or officials. Such sales would violate international sanctions aimed at cutting off North Korea from the global economy.
The investigation started this year after the police received information from a foreign law enforcement partner about a different matter.
After months of “careful and methodical” investigation, the police said, they uncovered evidence that led them to believe that Mr. Choi was working to generate income for the North Korean government from abroad as recently as this year.
If he is found guilty, Mr. Choi could face up to 10 years in prison.
“He seems to be a fellow traveler willing to take the risk to try and exploit whatever loopholes exist with surveillance and sanctions,” said Euan Graham, the director of the international security program at the Lowy Institute. “It means the North Koreans are still trying to access whatever componentry they can, even in a high-risk country like Australia.”
For years, North Korea has found ways to skirt sanctions to obtain technology and earn hard currency by selling not just weapons but also counterfeit money and drugs.
North Korea no longer has an embassy in Australia in part because of one such moneymaking mission gone wrong: In 2003, the Pong Su, a North Korean cargo ship that ran aground on an Australian beach, was found to be filled with about 275 pounds of heroin. The crew was arrested and later deported, and the North Korean embassy closed five years later.
When North Korea asked for it to be reopened in 2013, Australia refused.
Mr. Gaughan, the police official, called Mr. Choi’s arrest a sign of Australia’s commitment to upholding international sanctions on North Korea.
“This investigation shows that the United Nations and Australian sanctions will be rigorously enforced in Australia,” he said.