An Australian man once described as a "loyal agent of North Korea" pleaded guilty Wednesday to attempting to broker arms, oil and coal deals for Pyongyang in breach of international sanctions.

North Korea is under tough curbs aimed at choking off revenue to its nuclear and missile programmes.

South Korean-born Chan Han Choi was on trial in the New South Wales Supreme Court when he pleaded guilty to two of the seven charges against him.

Prosecutors withdrew the remaining charges -- including those relating to weapons of mass destruction -- and the jury was discharged.

Court documents showed Choi pleaded guilty to contravening a United Nations sanction enforcement law in late 2017 by brokering the sale of goods including arms and refined petroleum on behalf of North Korea.

He also admitted to contravening sanctions by brokering the sale of coal from North Korea to entities in Indonesia during the same period.

Public broadcaster ABC reported none of the alleged transactions was successful.

"We're very relieved that a more rational array of charges are now facing Mr Choi," his lawyer Mark Davis told reporters outside court.

Police, who arrested Choi in 2017, described him as "loyal agent of North Korea, believing he was acting to serve some higher patriotic purpose".

Davis told reporters outside court that Choi was "rejecting the military implication" and had been in business previously when it was legal to sell North Korean products.

Choi's case marked the first time charges were laid for violating UN sanctions against North Korea in Australia.

He was allowed to remain on bail and is due back in court next month.