S.Africa's Zuma courts workers on May Day

South African president Jacob Zuma raises his fist as he addresses supporters at Peter Mokaba stadium in Polokwane on May 1, 2014. By Gianluigi Guercia (AFP)

Polokwane (South Africa) (AFP) - South Africa's President Jacob Zuma on Thursday urged workers celebrating May Day to vote for the ruling ANC in a final push to bolster his re-election bid in next week's polls.

Addressing a lacklustre crowd affiliated with the Congress of South African Trade Union (COSATU), Zuma pledged to support workers' rights if re-elected to a second term in office.

"Workers of this country must know that in the ANC lies their future," the South African leader told the semi-empty stadium in the northern town of Polokwane, in Limpopo province.

Labourers form a crucial part of the ruling party's grassroot support base and COSATU is used to mobilise for votes.

But Zuma also used Thursday's rally to criticise the frequent strikes that have crippled South Africa's mining sector over the past three months, saying workers should return to their jobs.

"Unions must be alive to the realities that endless strikes are not in the interest of the workers and not in the interest of the economy," Zuma told the crowd of around 15,000, many of whom left during his speech.

"I think we should all agree that the time has come for the situation on the mines to change," he said.

The ruling African National Congress has won every election since South Africa's first all-race polls in 1994, and is almost certain to win again in the May 7 vote.

But rampant unemployment, poverty and corruption have hurt the party's image, prompting predictions it could face the most serious hit to its power in twenty years.

Zuma, who was first elected in 2009, has also personally come under fire for using public funds for multimillion-dollar renovations to his private home.

The public ombudsman ruled that parts of the upgrades were unlawful, ordering Zuma to pay for them.

Angry residents booed the president and stoned cars during another rally in Limpopo province earlier this month, local media reported.

COSATU secretary general, Zwelinzima Vavi, on Thursday told crowds in the southern city of Port Elizabeth that "South African workers were among the worst paid, if not the least paid worldwide".

And while he pledged to support the ANC, he also bemoaned "serious" corruption within the party and its alliance partner, the South Africa Communist Party (SACP).

"You don't have to go elsewhere to find corruption, it's here at home," he said.

"It's not that we hate the ANC, but its leadership's values and integrity."