A gunman has been sentenced to death for the murder of an American teacher in the capital of West Africa.

Mohamed Abdallahi Ould Ahmednah killed Christopher Leggett, 39, in the capital city of Mauritania, not far from the school he helped run.

Ahmednah was part of a trio who were alleged members of the al Qaeda's North African wing. Sidi Mohamed Ould Bezeid was jailed for 12 years and Mahmoud Ould Khouna for three years, both for complicity in the murder.

Al Qaeda's branch in the Islamic Maghreb took credit for the killing, and said Leggett was shot because he was trying to convert Muslims to Christianity.

The three men were also convicted of belonging to a terrorist organization and having "attacked Mauritania."