Police in Tanzania say they have arrested a number of people suspected of murdering old women in the belief that they were witches.
"Some of the suspects we are holding have confessed to killing these old women," the Shinyanga regional police commander, Mr Abdallah Missika, told the BBC Focus on Africa programme.
With "witchcraft"-related crimes on the increase in Tanzania, the police chief said old women with red eyes were being singled out for attack.
Police also arrested a number of witchdoctors suspected of passing on the names of "witches" to people whose relatives had died "through witchcraft".
"It is believed that any aged, old woman with red eyes is a witch," Mr Missika said.
The police chief also said that some of the suspects said they had been contracted to carry out the murders.
"They have confessed about people who have contracted them, either by paying them in cash, or in the form of cattle," said Mr Missika.
He confirmed that one of witchdoctors arrested on suspicion of identifying the witches was holding a firearm illegally.
Witchcraft is increasingly worrying the Tanzanian Government - in July the government exhibited human skin at an international business fair as part of a crackdown in the south of the country.
The head of the forensic science division in the chief chemist's office, Gloria Machube, said human skin was used in witchcraft rituals.
According to police, the skins are transported to Malawi, Zambia, Mozambique, South Africa and the Democratic Republic of Congo before reaching their final destination in West Africa.
In 2001 police broke a skin-smuggling ring and 13 people were charged with murder.
A total of six young people were suspected to have been killed and skinned in the Mbeya region of south-western Tanzania.
The prices of the human skins range from $2,400 to $9,600, depending on the age of the victim, police said.