An 83-year-old American nun has been kidnapped in Burkina Faso.

The bishop of the northern Kaya diocese said armed men took her from a nunnery where they vandalised rooms and sabotaged a vehicle.

The nun had served in the parish since October 2014.

A search operation is underway in the area bordering the Soum province where attacks on civilians have increased and where armed groups are active.

Several Westerners have been abducted by Islamist militants in northern Burkina Faso and other parts of the Sahel in recent years.