Sergei Stepura, head of the Federal Security Service (FSB) Directorate for the Arkhangelsk Region, said the countries involved included the United States, some of its NATO allies, and specific Asia-Pacific states.
Located in Severodvinsk on the White Sea, Sevmash is Russia's largest shipyard and builds nuclear-powered submarines, oil and gas platforms and tankers.
Stepura told a news conference at RIA Novosti that several foreign intelligence agents, as well as persons suspected of working on behalf of foreign intelligence agencies, had been "spotted around sensitive areas."
He said a criminal case had been opened against a regional law enforcement officer under the provisions of the Official Secrets Act.
Stepura also said there was still the danger of terrorist attacks on nuclear and other hazardous facilities in the region.
He said two explosive devices, 16 firearms and 138 rounds of ammunition, as well as more than 6 kilograms of mercury, had been seized in the region this year.