An official in Burundi says the withdrawal of 1,000 Burundian soldiers from the African Union regional force in Somalia has begun.

The military official in Burundi, who insisted on anonymity because he is not authorized to speak to the press, said Thursday that about 200 soldiers boarded a flight from Somalia to Burundi's capital, Bujumbura, in the afternoon.

More soldiers are expected to be flown back from Burundi in the coming weeks.

The African Union says it plans to withdraw the 21,500 troops that it has in Somalia by the end of 2020. The AU force, made up of soldiers from several African countries, has for years tried to secure the Horn of Africa country against the Islamic extremist rebels of al-Shabab.