Prosecutor Milana Digayeva demanded that 63-year-old Frode Berg serve the sentence in a strict penal camp, according to the Interfax news agency.

The verdict is expected on April 16, she said.

The hearing was held behind closed doors and Berg rejected the charges against him.

Berg was detained in Moscow in 2017 following a sting operation by Russia's FSB security service.

A former Russian police officer was accused of handing Berg files on the Russian navy and given a 13-year prison term in December.

Berg admitted to acting as a courier for the Norwegian intelligence services several times, but said he thought he was only shuttling money.

Norway, a NATO member, normally enjoys good relations with neighbouring Russia, with which it shares a short land border.

But these have grown more tense since 2014, when Russia annexed Crimea and a pro-Russian insurgency erupted in eastern Ukraine.