A Russian nuclear submarine that was under repair in a far northern port has caught fire, but officials said there was no danger of radioactive emissions or explosion.

The fire broke out in the Zvezdochka shipyard in Severodvinsk, about 1,000 kilometres north of Moscow on the White Sea.

The state news agency Tass said the ship that caught fire was the Orel, an Oscar II-class submarine that is capable of carrying nuclear-tipped cruise and anti-submarine missiles.

Ilya Zhitomirsky, a spokesman for the United Shipbuilding Corporation which runs the shipyard, said the submarine's weapons and critical elements of its nuclear reactor had been removed before the repairs started.

He told the Associated Press that no one was injured in the fire, which he said started in the vessel's insulation.