(Adds COSATU, ANC comments)
JOHANNESBURG, Dec 3 (Reuters) - South Africa's government launched a widely unpopular road toll around the economic hub of Johannesburg on Tuesday, a move likely to heighten tensions with its union allies and alienate some voters in the run-up to next year's elections.
The electronic levies, known as e-tolls, have fuelled public anger and strained relations between President Jacob Zuma's African National Congress (ANC) and COSATU, the labour federation that has supported the ruling party since the end of apartheid in 1994.
"E-tolls will have a serious impact on elections. It's not too late for Zuma to scrap the system," said COSATU provincial spokesman Dumisani Dakile at the launch of a campaign urging commuters to boycott the toll.
The ANC has urged motorists to register for the tolls and not to embark on "lawlessness".
Despite threats of violent protests and a last-minute legal attempt to block the start of the tolls, the new system went live with few immediate problems.
Traffic was light on several motorways around Johannesburg as some commuters attempted to avoid tolls by using back roads, while others made rude gestures as they drove through the tolling gantries, local media said.
The tolls on motorways in and around Johannesburg and the capital, Pretoria, will go towards repaying a $2 billion loan used to finance extensive upgrades to Africa's busiest road network.
The government says those who refuse to pay will face criminal prosecution. Ratings agencies and bond investors are watching the roll-out of the scheme closely since the Treasury will have to foot the bill if it fails. (Reporting by Xola Potelwa and Peroshni Govender; Editing by Stella Mapenzauswa)