JOHANNESBURG (Reuters) - Violent protests in South African townships spread on Wednesday, piling pressure on President Jacob Zuma to deliver on government promises of help for the poor three months after elections.

Protesters pelted cars with stones and blocked a highway near Johannesburg in the worst disturbances since Zuma took office, intensifying uncertainty after a wave of strikes and threats of industrial action in Africa's biggest economy.

The unrest also undermines South Africa's hope of showing a positive image with less than a year to go before the World Cup finals.

Residents in Meyerton, south of Johannesburg, occupied farmland in invasions reminiscent of those in neighbouring Zimbabwe. They were protesting at being evicted from their temporary settlement.

Protests continued in Johannesburg's volatile Thokoza township, where residents demand better housing and services. Thirty-five residents are due to appear in court there on Wednesday after protests turned violent on Tuesday.

In the northeastern region of Mpumalanga, residents in Balfour threatened to burn down municipal offices if 100 people arrested in protests on Tuesday were not released, Talk Radio 702 said.

Poor South Africans complain they have not seen the benefits since white minority rule ended 15 years ago. Zuma pledged to do more to help them as the main plank of the election manifesto of the ruling African National Congress.

But the government is limited by South Africa's first recession in 17 years, as a result of the global crisis, and is wary of any policies that might discourage local or foreign investment.

Trade unions, whose support was instrumental in Zuma's rise to power, have also been flexing their muscles since he took office, with stoppages to demand more pay and threats of strikes in the world's top platinum producer, also an important gold miner.

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