SEOUL (AFP) - South Korea stepped up its legal battle against Uber on Thursday, with its telecom watchdog reporting the web-based taxi company to prosecutors for violating communications rules.

The move came a month after prosecutors indicted Uber's American founder and chief executive Travis Kalanick and its Korean partner MK Korea for operating an illegal cab service.

The Korea Communications Commission (KCC) ruled that Uber Korea had failed to report its business and receive official permission before providing its location tracking services. "The commission decided to refer Uber to prosecutors because it has no legal status," a KCC official told AFP.

Uber started its service in Seoul in 2013, sparking angry protests from South Korean taxi drivers.

The Seoul city government has filed separate complaints with prosecutors, saying Uber's operations raise passenger safety issues and threaten the livelihoods of licensed cabbies.

City regulators have launched a crackdown on drivers that cooperate with Uber, with a 1 million won (S$1,230) reward offered for those who report cars offering rides through the Uber service.

Uber is the most prominent of several smartphone apps that are shaking up the traditional taxi landscape in cities around the world.

But it faces criticism and significant resistance from regulators in several countries, who accuse it of unfair competition and a lack of standards.