There is also a separate ethnic Korean community on the island of Sakhalin, typically referred to as Sakhalin Koreans. Some may identify as Koryo-saram, but many do not. Unlike the communities on the Russian mainland, which consist mostly of immigrants from the late 19th century and early 20th century, the ancestors of the Sakhalin Koreans came as immigrants from Gyeongsang and Jeolla provinces in the late 1930s and early 1940s, forced into service by the Japanese government to work in coal mines in Sakhalin (then a part of the Empire of Japan as Karafuto Prefecture) in order to fill labour shortages caused by World War II.