Pakistan, Sept. 10 -- NATO forces tracked Russian submarines during a covert operation near Norway's Svalbard archipelago earlier this year. Western officials said the vessels tested technology designed to damage critical undersea cables. The operation reportedly involved Russia's secretive deep-sea warfare unit, known as GUGI. Britain, Norway and the United States monitored the Russian vessels during the operation. No undersea cables were damaged during the incident.

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Two Western officials told Reuters that Russian deep-sea submersibles were rehearsing possible use of the technology. They said the equipment could potentially be deployed during a future conflict with NA...