By Ed Stoddard and Tiisetso Motsoeneng
PRETORIA/JOHANNESBURG (Reuters) - More than 30,000 people marched in South Africa's capital Pretoria on Wednesday calling on President Jacob Zuma to quit, keeping up pressure from the streets on the leader over his handling of the struggling economy.
The protesters marched through the city and held a rally at a field outside the Union Buildings, the site of Zuma's offices.
Zuma, who turned 75 on Wednesday, has survived previous protests. But the main opposition party Democratic Alliance (DA) and other parties behind the protest believe they can drum up support to force Zuma out of office following his dismissal of respected Finance Minister Pravin Gordhan in a cabinet reshuffle.
South Africa's economy has grown lethargically over the last six years and the jobless rate stands near record levels. Analysts say the political crisis is making it hard to reform the economy, improve social services and fight crime.
The ruling African National Congress (ANC) party has rejected calls for Zuma to step down. He has denied repeated allegations of corruption since winning power in 2009. More than 60,000 people marched on Friday calling for him to quit.
The ultra-left Economic Freedom Fighters and other parties took part in Wednesday's protest, dubbed "National Day of Action".
"He is misusing state money," said 21-year-old student and Pretoria resident Thomas Monyoko wearing a red EFF T-shirt.
"Let the message be clear today that Zuma is no longer a credible president of South Africa," Economic Freedom Fighters leader Julius Malema said. "We don't care whether you are white, whether you are Indian, whether you are black, we are here to defend the future of our children."
Zuma had accused Friday's marchers of having racist motives. Like Friday, a mixed racial profile of people attended Wednesday's rallies but there were less white people.
Patricia Maguire, a white 40-year-old risk analyst who also took part in Friday's protest, held a sign saying: "Recall The Wrecking Ball," referring to Zuma.
"I don't think this is a party thing, it is a governance issue. I can't see how anyone cannot see that he is critically destructive," said Maguire, who said she had no party affiliation.
In another development, parliament said a motion of no-confidence in Zuma called by the opposition had been postponed until a court decided whether the vote should be taken by secret ballot.
Opposition parties requested the delay. The parties have said the vote could have a chance of success if it is held by secret ballot, but the ANC has said it will vote against it.
Zuma's office said he was expected to hold a cabinet meeting to discuss the economic situation after Fitch and S&P Global Ratings last week downgraded South Africa to "junk", citing Gordhan's dismissal as one reason.
Zuma meanwhile sang, danced and cracked jokes at his 75th birthday celebrations held in Soweto township, near the commercial hub of Johannesburg.
Thousands gathered under a large tent, while others outside made merry, some performing the high-stepping "toyi toyi" dance as pro-Zuma and anti-apartheid tunes blasted from huge speakers.
"I'm not worried when people call me names. I've been called names for years," said a jovial Zuma, speaking in the Zulu language. "The opposition are doing their job, which is to oppose, don't be worried," he told supporters.
Wrapping up his speech, Zuma said: "If tomorrow you (ANC) say that I should step down, I will do so with a pure heart."
Rachel Mokgatshwane, 73, said she was there to support Zuma and wish him a happy birthday.
"We get our welfare payouts in time. I don't complain," she said.
Another ANC supporter, Patrick Nyende, 54, said: "We don't see any reason for him to step down. None."
The rand climbed to a one-week high on Wednesday, in part encouraged by comments from the new finance minister indicating no significant change in policy.
Finance Minister Malusi Gigaba has sought to reassure investors since Gordhan was sacked.
Nomura analyst Peter Attard Montalto said: "There is a general question about where South Africa is going."
But he added "The probability of Zuma's exit is low at just 20 percent."
(Additional reporting by James Macharia, Nqobile Dludla and Lynette Ndabambi in Johannesburg, Writing by James Macharia, Editing by Angus MacSwan)