Men in parts of Tanzania's main city, Dar es Salaam, are living in fear of a night-time sex attacker.
Some believe a bat turns into a man at night
A BBC correspondent says the attacks are being blamed by some on a demon called "Popo Bawa" meaning winged bat.
Some men are staying awake or sleeping in groups outside their homes. Others are smearing themselves with pig's oil, believing this repels attacks.
Reports of the demon's existence have been common for many years in Zanzibar, where locals claim it originated.
The BBC's John Ngahyoma in Dar es Salaam says not many people actually believe that the demon exists and there have been no sightings.
But Mbaruku Ibrahim, who hails from Zanzibar, says the story of the demon is common there and people in his village on Pemba island sleep beside a huge fire outside their houses whenever it is said to appear.
The story goes that the bat is able to transform itself into a man at night and it has also been blamed for rapes of women.
Sheikh Yahya Hussein, a prominent astrologer in Tanzania, claims that the demon is a spirit that is unleashed by witches to torment their opponents.
Belief in witchcraft and superstitions is widespread in Tanzania, especially in rural areas.