JOHANNESBURG (AFP) - South African authorities on Tuesday rolled out a highly unpopular electronic tolling of highways in and around Johannesburg, drawing the ire of motorists in the run-up to next year's election.

The decision has further strained ties between the ruling ANC party and its main ally, the Congress of South Africa Trade Unions (Cosatu).

The Cosatu described the launch day as "Black Tuesday for the poor and the working class" and "a turning point for the democratic state and government".

Cosatu, a crucial source of political support and votes for the ANC, warned that the party risked losing votes on 2014 elections and "will regret" its decision.

"Many loyal supporters of the movement will not go to the polls due to this unjustified and unfair system," said provincial secretary Dumisani Dakile, suggesting some politicians in the ANC were now "power drunk".

The labour movement vowed to step up its campaign to have the tolls scrapped by staging hunger strikes, sit-ins and protests.

The main opposition Democratic Alliance seized the opportunity to boost its election campaign, launching an anti-electronic tolls sky banner carrying the inscription "fight e-tolls - vote DA" flown across Johannesburg during peak traffic periods.

"The best way to fight e-tolls is to vote against the party that introduced it," said Mmusi Maimane, the DA candidate running for the post of provincial premier for Gauteng.

The DA which already controls Cape Town and the surrounding province and has its eyes set on wresting control of Gauteng from ANC in the 2014 vote.

Religious groups has also joined the fight, urging followers not to buy e-toll tags, because it "is like selling your soul to the devil".

The government argues that fees, capped at 550 rands (S$67) are needed to pay for highway upgrades.

The system is operational on the 185km stretch between Johannesburg and the capital Pretoria.

A group of 15 Christian church leaders declared in a statement that they refused to pay the "unjust" e-tolls and called "on all other church leaders, members of our churches and all South Africans who support democracy... to do the same." According to the alliance opposed to tolling, less than 40 per cent of road users had purchased electronic tolling tags which are fitted on cars.