ST PETERSBURG, Russia (Reuters) - President Vladimir Putin, asked about the risks of nuclear war over Ukraine, cautioned the West on Wednesday that Russia could use all available means to defend itself if its sovereignty or territorial integrity were threatened.

Putin said that the West had repeatedly accused Russia of nuclear sabre rattling but said this was wrong, and pointed out that it was the United States which had used nuclear weapons against Japan in World War Two.

Putin, speaking to senior editors of international news agencies in St Petersburg, said that Russia's nuclear doctrine permits such weapons to be used in response to a number of threats.

"For some reason, the West believes that Russia will never use it," Putin said. "We have a nuclear doctrine, look what it says. If someone's actions threaten our sovereignty and territorial integrity, we consider it possible for us to use all means at our disposal. This should not be taken lightly, superficially."

(Reporting by Reuters; Writing by Alexander Marrow/Guy Faulconbridge; Editing by Andrew Osborn)