SAO PAULO (AFP) - An Uber driver in Brazil's financial capital Sao Paulo responded to a call, only to find himself ambushed by a group of regular taxi drivers, a report said Monday.

Folha daily quoted the man as saying that he was responding to his eighth call of the night on Saturday, when instead of a client he ran into angry rivals.

Blocked by 20 official taxis, he tried to retreat, but was forced into a taxi and beaten as he was driven around Sao Paulo for half an hour, said the man, who was not identified.

Antonio dos Santos, president of the city's taxi union Simtetaxis, said that one of the assailants had been identified.

"You can't take justice into your own hands. The problem of these illegal (Uber) drivers has to be resolved through legal means," he said.

"The authorities should act to stop these undeclared drivers," said Natalicio Bezerra, from another union, Sinditaxi.

"If the authorities don't take the initiative, things could get worse."

Uber is increasingly popular in Brazil despite attempts to ban it, and major protests by traditional taxi drivers against the increasingly powerful online ride-booking service.