Autogenocide is the extermination of a country's citizens by its own people or government. Auto comes from the Greek reflexive pronoun while genocide comes from the Latin words gens meaning "race, tribe" and -cidere meaning "kill.
The term was coined in the latter half of the 1970s to describe the actions of the Khmer Rouge government of Cambodia, to distinguish such acts from the genocide of groups considered "other" by a government, such as the killing of Jews and people of Slavic origin by Nazi Germany.
One could also argue that it can be applied to any act of suppression that involves deaths and displacement of millions of hetereogeneous, such as the Stalinist Purges of the 1930s.
See also