Returning from a NATO exercise, the KNM Helge Ingstad frigate sank after crashing into the Maltese oil tanker Sola TS in the early hours of November 8, in a fjord near the western Norwegian town of Bergen.

Eight of the 137 people aboard the frigate received minor injuries.

A 33-year-old officer who had taken over the controls eight minutes before the collision was accused of negligence.

"He considers it unfair that he is the only one held responsible for the accident, since there was a combination of factors," his lawyer Christian Lundin said after the Bergen court announced its verdict.

The prosecution had called for a 120-day suspended sentence.

Norway's Accident Investigation Board had concluded the collision was largely due to human error.

The loss of the vessel deprives Norway's navy of one of the five frigates it had during a period of heightening tensions with neighbouring Russia.