Three Italian nuns were found killed in Burundi over the weekend, with two of them reportedly raped and decapitated.

The women were found dead at the Kamenge institution in a northern suburb of the capital, Bujumbura.

Reuters say three suspects had been detained for questioning over the incident.

It is not known what the motive behind the killings was, but reports suggest it could have been armed robbery.

Pope Francis has sent his condolences in a telegram to the archbishop of Bujumbura. The Holy See said he learned of the murders "with great sadness."

The nuns have been named as Lucia Pulici (75), Olga Raschietti (82) and Bernadetta Boggian (79).

Sr Pulici and Sr Raschietti were found decapitated in their dormitory on Sunday.

While Sr Boggian was found dead early on Monday morning. It is thought the killings may have happened at two separate times.