North Korea, officially the Democratic People's Republic of Korea (abbreviated as DPRK, PRK, DPR Korea, or Korea DPR), is a country in East Asia constituting the northern part of the Korean Peninsula. Pyongyang is the capital and largest city. To the north and northwest, the country is bordered by China and by Russia along the Amnok (known as the Yalu in China) and Tumen rivers; it is bordered to the south by South Korea, with the heavily fortified Korean Demilitarized Zone (DMZ) separating the two. Nevertheless, North Korea, like its southern counterpart, claims to be the legitimate government of the entire peninsula and adjacent islands. Both North Korea and South Korea became members of the United Nations in 1991.