Eleven elderly people accused of being witches have been burned to death by a mob in the west of Kenya, police say.

A security operation has been launched to hunt down villagers suspected of killing them in Kisii District.

The BBC's Muliro Telewa in the region says the gang had a list of the victims and picked them out individually.

The area has witnessed similar attacks in the past when people suspected of engaging in witchcraft have been killed or ostracised.

But our reporter says that this is a surprisingly large number of people to be attacked at the same time.