Kinyarwanda (also sometimes known as Rwanda language) is the native language of the Banyarwanda, and is spoken as a mother tongue by most Banyarwanda in Rwanda as well as those in the Congo and Uganda. Kinyarwanda is a Bantu language, and is mutually intelligible with Kirundi, an official language of Burundi and Ha, a language of western Tanzania; together, these languages form part of the wider dialect continuum known as Rwanda-Rundi. With more than 10 million Kinyarwanda speakers, and around 20 million for Rwanda-Rundi as a whole, it is one of the largest of the Bantu languages. The language was likely to have been introduced to the area from Cameroon during the Bantu expansion, although the timescale and nature of this migration is not known conclusively. It is likely that these migrations caused Kinyarwanda to replace the native tongue of the Twa, and the Tutsi may also have originally spoken a separate language, under the hypothesis that they migrated from Nilotic speaking regions.