It usually corresponds specifically to the three provinces of Liaoning, Jilin, and Heilongjiang but is sometimes also meant to encompass the northeastern portion of Inner Mongolia. The heartland of the region is the Northeast China Plain. It is separated from Far Eastern Russia to the north by the Amur, Argun, and Ussuri rivers; from North Korea to the south by the Yalu and Tumen Rivers; and from China's Inner Mongolian Autonomous Region to the west by the Greater Khingans.