The patrol by diesel-electric submarines began in early August, and the Russian sub involved, the Volkhov, covered around 2,000 miles during its voyage from its Vladivostok base, according to a statement from the Russian Pacific Fleet. The subs patrolled in the Sea of Japan and the East China Sea, the statement said. China has not confirmed the patrol, but the state-run Global Times mentioned it in a report Wednesday, citing the Russian reports.