On October 27, 1981, a Soviet submarine 137 surfaced in Swedish internal waters, well inside the military protection area of the naval base of Karlskrona. The submarine had grounded on a shoal and was unable to move without assistance. The Swedish Government refused a request from the USSR to salvage the ship itself and demanded that, in return for assistance by Swedish vessels, the commander submit to interrogation by Swedish authorities. The Soviet Union acceded to this by a formal agreement. The submarine was eventually escorted out of Swedish territorial waters.