"This case is like nothing we have ever seen on Australian soil," Australian Federal Police Assistant Commissioner Neil Gaughan.

"This is the first time charges have been laid under the Commonwealth Weapons of Mass Destruction Act in Australia, and the first time we have laid charges specifically for alleged breaches of UN sanctions against North Korea."

Choi is facing six charges in connection with the acts. The maximum penalty for the offenses is 10 years' imprisonment, police said.

He didn't appear or apply for bail during court on Sunday, and bail was formally refused by Acting Magistrate Carl Milovanovich, the CNN affiliate reported. He's due to appear in court on December 20.

Police started investigating the suspect after a tip "from another international agency on another matter."

According to the Seven Network report, Gaughan said the business activity occurred offshore and that "there had been no risk to the Australian public and that no weapons, or missile componentry -- which he said was software-- had been imported into Australia."

"This man was a loyal agent of North Korea, who believed he was acting to serve some higher patriotic purpose," Gaughan said, according to Seven Network Australia.

"I think at the end of the day he would sell whatever he could to make money back for the North Korean government."

Gaughan told reporters Choi had been charged over two transactions that were unsuccessful, and there may have been others.

"But we estimate that if these trades were successful we're talking tens of millions of dollars," he told reporters in Sydney.

Suspect was on police radar

Police allege that Choi:

• "Provided services to a Weapons of Mass Destruction Program and discussed the sale of specialist services and ballistic missile technology, with a view to generating income for the North Korean regime."

• "Those discussions have included the establishment of a ballistic missile production facility, the supply of missile construction plans and the provision of North Korean technical specialists for training and development outside of North Korea."

• "He discussed the possible sale of missile guidance systems in an effort to generate further income for North Korea."

Gaughan said Choi had been under investigation for months. AFP officers conducted search warrants in Sydney on Saturday and the man was "subsequently arrested" in the Sydney suburb of Eastwood.

"The Australian public should be assured that police have acted to ensure no direct risk to our community. The AFP endeavours to support international efforts to maintain peace and security," Gaughan said in the police statement.

"Any individual who attempts to fly in the face of sanctions cannot and will not go unnoticed in Australia."

More charges against the man have not been ruled out, according to the police statement.

Australia relations with North Korea

Australia is a US ally and its government has voiced support for the United States' policy on North Korea.

Pyongyang has continually assailed Australia as a "vassal country" of the United States in recent releases from North Korean state media.

In early October, a spokesman for the North Korean Foreign Ministry told the country's state-run Korean Central News Agency (KCNA) that Australia's support for the United States in opposing North Korea was a "suicidal act."

"Australia will be unable to avoid a disaster if it keeps toeing the US line of military, economic and diplomatic pressure upon the DPRK despite its repeated warnings," the Foreign Ministry spokesman was quoted as saying.

"It should be prudent in speech and conduct with its own principle, instead of blindly following the US' policy of aggression, and realize that working to develop friendly relations with other countries is the best way to its security."

Australia was one of a number of countries addressed in an open letter from North Korea in October, in which Pyongyang accused the US of declaring war.

"I see it as evidence that the collective strategy of imposing maximum diplomatic and economic pressure through sanctions on North Korea is working," Bishop said.

The Australian navy held joint military exercises with its South Korean and US counterparts off South Korea's coast in November.

South Korea has been a long-term ally of the United States, since the two states fought together during the Korean War in the 1950s.