The suspect was detained Monday at Oslo’s international airport as he returned from China, Thomas Blom, a spokesman for the service’s counter-espionage unit, told reporters.

An Oslo court placed him in four-week pre-trial detention with a ban on communicating with the outside, and with the first two weeks to be spent in isolation.

A lawyer for the man, whose identity has not been revealed, said he denied the charges against him.

“He says he is innocent and that he is not an agent for China,” the lawyer, Marius Dietrichson, told AFP.

He said he could not provide further details because of the sensitive nature of the accusations.

The security services have not provided details on what information the suspect might have provided to China.

“We are in a preliminary and extremely sensitive phase,” Blom told reporters as he left the Oslo court.

“We are at the very preliminary stage where we are gathering the evidence.”

The Chinese embassy in Oslo did not respond to requests for comment.

In their annual evaluation of the risks facing Norway, the country’s security services said China and Russia were the two major threats in terms of espionage.

The growing threat from China is due to “the deteriorating relations between China and the West, China’s desire for greater control over supply chains and its interest in the Arctic,” the report said.

Norwegian authorities are currently seeking to prevent the sale of the last piece of private property in the Arctic archipelago of Svalbard.

According to a lawyer representing the owners, a Chinese group had expressed interest in the 60 square-kilometre (23 square-mile) domain.