African leaders have appointed Zimbabwean President Robert Mugabe as the new chairman of the 54-nation African Union.

The 90-year-old, who has ruled his country since 1980, succeeds Mauritania's President Mohamed Ould Abdel Aziz.

The announcement was made during the African Union's two-day heads of state summit at the organisation's headquarters in Ethiopia's capital.

Traditionally, the chairmanship is given to the leader of the country hosting the next summit, but exceptions have been made.

For example, in 2005, it was the turn of Sudan's Omar al-Bashir - but African leaders bowed to outside pressures in the uproar over killings in Darfur. They passed over Mr al-Bashir and instead kept Nigeria's Olusegun Obasanjo for a second year.