Norway’s security police PST has charged a DNV GL worker with spying after he admitted selling information to Russia.

The unnamed staffer in his 50s was arrested in an Oslo restaurant on Saturday while having dinner with a Russian intelligence officer, according to PST.

The security police tweeted: "PST arrested a Norwegian citizen in Oslo on Saturday 15 August.

"The man is accused of having handed over information to a foreign state that could harm basic national interests."

He appeared at Oslo city court on Monday, when he was remanded in custody for four weeks as the probe continued.

"We have detained a man his 50s, suspected of sharing information with a Russian intelligence officer. We consider this to damage fundamental Norwegian interests," police attorney Line Nygaard told state broadcaster NRK.

NRK reported the man had received "considerable amounts of cash" for information.

"The arrest took place in a restaurant in Oslo without any drama," Nygaard told reporters.

Denies criminal act

The accused has denied criminal liability.

His lawyer Marianne Darre-Naess told NRK that her client says his actions are "more nuanced" than the charges against him.

PST said it believes the man has had contact with a Russian agent over a long period.

The government is not commenting on the likely fate of the Russian national in the case.

DNV GL confirmed the accused had been employed at the classification society for several years, working in the defence sector.

The company is cooperating with PST. "We’ll be working closely with the police to assist in their investigation," it said.

"This is an extremely serious case and we need to get to the bottom of it."