Bruno Borges de Oliveira
Bruno Borges de Oliveira, 18, was beaten to death in Sao Paulo, BrazilFacebook

Police in Brazil's largest city of Sao Paulo have arrested a gang of skateboarders who beat a gay teenager to death in what authorities said was one of a series of punitive robberies targeting homosexuals.

The six suspects, aged between 16 and 23, confessed to killing 18-year-old Bruno Borges de Oliveira, police said.

De Oliveira died of injuries suffered during a brutal early-morning mugging in central Sao Paulo.

He was stripped of his shoes, mobile phone, and public transport ticket before being punched, kicked and repeatedly hit on the head with a skateboard.

He was on his way home after a night out in the famous LGBT Frei Caneca Street. Friends fled the assault and alerted police.

"When we came back he was already dead," one friend, who has not been named, told G1 Globo website.

Police said that the gang had previously targeted homosexuals. The skateboarders allegedly carried out a series of dawn raids against people leaving gay nightclubs in recent weeks.

"They chose their victims for being gay," police spokesman Ruy Ferraz Fontes told Folha de Sao Paulo newspaper. "They stole the victim's belongings as part of a ritual of humiliation."

On the same night that De Oliveira was killed, at least another three people were mugged by the gang, police said.

"They tried to surround me and punched me," one victim said. "I have no doubt this is the result of homophobia."

Authorities have released photos of the suspects and said they expected many more victims to come forward.