A Brazilian investigative reporter who was following leads in a drug-dealing and child prostitution case has been found decapitated in the south-eastern state of Minas Gerais.

"The union is demanding a rigorous investigation. Independent journalist Evany Jose Metzker was warned he ran a risk investigating drug trafficking and child prostitution in this violent region," said a spokesman for Brazil's journalists union.

The union denounced what it termed an attack on freedom and the right to inform.

Mr Metzker, 67, had been working on a series of stories for three months in the Jequitinhonha Valley, one of Brazil's poorest regions.

The reporter had been missing for five days before his bound, badly marked and decomposing body was found on Monday, police said.

Extra, a popular daily newspaper, quoted Metzker's family as saying an anonymous tip off had led police to the body.

An initial autopsy carried out in the nearby town of Teofilo Otoni was unable to establish the cause of death and the body was transferred to state capital Belo Horizonte for further tests.

AFP