(Updates with Norwegian comment on radioactivity levels)
MOSCOW, July 27 (Reuters) - A surge in air pressure damaged a ballast tank on a Russian nuclear submarine during repairs but the incident was minor, Interfax news agency quoted a navy spokesman as saying on Friday.
The agency had earlier quoted an official in the local administration as saying there had been a small blast.
In nearby Norway, the radiation protection agency said Norwegian sensors did not detect any change in radioactivity levels.
"We have had no indication that this incident involved any radioactive releases," Ingar Amundsen, head of the environmental protection section at the Norwegian agency, told Reuters.
Russian navy spokesman Igor Dygalo said there was no explosion and no one was hurt in the incident at a dockyard in the White Sea port of Severodvinsk.
"The management of the (dockyard) ... considers the accident as minor," Interfax quoted Dygalo as saying. He said the damaged cistern will be soon repaired.
Interfax quoted the local environmental monitoring agency as saying that the background radioactive level in the area did not exceed natural levels.
It is normal practice in the Russian navy for submarine reactors to be shut down and the fuel removed when they are in dry dock for repairs.
Russia’s has a history of incidents — some of them fatal — in its submarine fleet. Modernisation is under way, but many of the vessels have been in operation beyond their normal service life.
In the worst incident of the past few years, the Kursk submarine sank to the bottom of the Barents Sea on Aug 12, 2000, after two explosions on board. All 118 crew members died.
In September last year, a fire on board the submarine St. Daniel of Moscow, moored near the Finnish border, killed two crew members. (Additional reporting by Wojciech Moskwa in Oslo and David Cutler in London)