Documents that showed plans for a submarine-launched nuclear torpedo were accidentally shown on Russian state TV, the Kremlin has admitted.
The video showed a document over the shoulder of an army official that described a weapons system called Status-6 (pictured).
It said the weapon would cause radioactive contamination to make coastal areas unsuitable for military or economic activity ‘for a long time’.
The shot was taken during a meeting with President Vladimir Putin, and broadcast on NTV and Channel One, which is state controlled. The channels later removed the footage.
The appearance of the video on a channel controlled by the Kremlin caused some to speculate that it was leaked intentionally in order to alarm the West.
A spokesman for Putin, Dmitry Peskov, said: "It's true that some secret information was caught by the camera and therefore it was subsequently removed. We hope this will not happen again."
Mr Putin has held four meetings on defence issues this week, reflecting the close attention he is paying to military modernisation at a time of heightened tensions with the United States and Europe over the crisis in Ukraine.
At Monday's meeting, he said Russia's military modernisation programme had been successfully implemented, with defence plants churning out new jets, missiles, navy ships and other weapons.
Last year, the Russian military successfully tested a missile that was reportedly capable of striking with 100 times the force of the Hiroshima atomic bomb.
It was launched from a submarine in much the same fashion as that shown in the leaked documents.