"There is one lesson from all this. If you fight, you will always win"

Alexander Nikitin

It rejected an appeal by prosecutors to reopen the case against Alexander Nikitin, 46, who was acquitted last year.

The court's ruling is final and puts an end to the case which attracted international attention from environmentalists and human rights campaigners.

Mr Nikitin was arrested in 1996 after he contributed to a report by the Norwegian environmental group Bellona on the dangers posed by radioactive pollution in the Arctic seas.

Kursk theory

"I feel fantastic," said Mr Nikitin after leaving court.

"This has dragged on for nearly five years, and at long last we've reached the end.

Sea samples are tested in Norway for radioactivity after the Kursk sank

"It's not just a personal victory, it's even more important for others.

"There is one lesson from all this. If you fight, you will always win."

Mr Nikitin, who had faced a possible 12-year jail term, said the information - including allegations that the Russian navy improperly stored and dumped nuclear waste - was of environmental importance and was not subject to Russian secrecy laws.

Mr Nikitin has also speculated about the causes of the Kursk's sinking, adding his voice to theories that an onboard explosion caused the disaster.

"A torpedo must have exploded on board the Kursk," he said.

"Tests involving had been carried out on the Kursk , notably by two specialists, one of whom was a civilian."

In addition to his revelations about radioactive pollution, Mr Nikitin also provided Bellona with information about safety systems for naval nuclear reactors and details of Soviet nuclear submarine accidents.

Prosecutors say this amounted to high treason, but Mr Nikitin and Bellona say the information was of environmental importance, and not subject to Russian secrecy laws.