The murders of thirteen gay men over a period of 18 months in a suburban park in the Brazilian city of Sao Paulo may be the work of a serial killer.

Police are investigating links between the crimes and have stepped up nighttime patrols in the park, which is known as a cruising ground.

All the victims were aged between 20 and 50.

One died from blows to the head – the other 12 had been shot.

Police are carrying out tests to determine if the same gun was used in all the attacks.

“The case now has gone beyond the limits of such common crime,” local police chief Paulo Fernando Fortunato told Folha de Sao Paulo newspaper.

“We are dealing with a suspect who kills homosexuals, exclusively.

“In his mind, he’s cleaning up the place. He doesn’t like, he hates homosexuals.

“Who is he? We don’t know.”

The police chief said he went public to try to save lives.

The first body was found in July 2007 and the most recent in August this year.

Police have reportedly dubbed the serial killer suspect the Rainbow Maniac, a reference to the multi-coloured Pride flag, an international symbol of the gay community.