* Protesters to hold rallies outside Zuma's offices
* Opposition drumming up support for no-confidence motion
* Ruling ANC party backs Zuma, rejects call for him to quit
* Zuma to hold cabinet meeting, own birthday celebrations
By Ed Stoddard
PRETORIA, April 12 (Reuters) - Several thousand people gathered in South Africa's capital on Wednesday to protest against President Jacob Zuma following a much-criticised cabinet reshuffle, days after the opposition called countrywide marches to demand his resignation.
The protesters plan to march through the city's streets to hold a rally at a field outside the Union Buildings, the site of Zuma's offices. More than 60,000 people marched on Friday calling for Zuma to quit, with the president accusing some of the protesters of racist motives.
Africa's most industrialised 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.
Zuma, who turns 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 after he dismissed respected finance minister Pravin Gordhan in a cabinet reshuffle.
The ultra-left Economic Freedom Fighters and other smaller parties are also taking part in the protest dubbed "National Day of Action". The opposition has called for a no-confidence vote against Zuma in parliament on April 18.
The ruling African National Congress party, which has a majority in parliament, has rejected calls for Zuma to step down and said it will vote against the no-confidence motion.
"Rain will not stop us because we want the president to step down, he is misusing state money," said 21-year-old student and Pretoria resident Thomas Monyoko wearing a red EFF T-shirt after rainfall lashed the city earlier in the day.
Zuma has denied repeated allegations of corruption since winning power in 2009, and survived four previous no-confidence votes in parliament.
"Let the message be clear today that Zuma is no longer a credible president of South Africa," EFF leader Julius Malema told the crowd before it started marching to Zuma's offices.
A group of EFF activists carried a coffin draped in the South African flag. One of them who declined to give his name said "it is Zuma, he is finished today". Hundreds of boisterous EFF supporters bussed in shouted "Zuma must go!".
Patricia Maguire, a white 40-year-old risk analyst on her way to the march who also took part in Friday's protest in Pretoria, 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, while on a Pretoria bound train from Johannesburg.
Nomura analyst Peter Attard Montalto said: "There is a general question about where South Africa is going ... the probability of Zuma's exit is low at just 20 percent."
Like Friday, a mixed racial profile of people attended Wednesday's rallies, but there were less white people.
Zuma's critics have said his comments about racist language used on placards at Friday's protests were an attempt to deflect attention.
The ANC and the party's influential Women's League expressed their support for Zuma.
His office said on Wednesday the president would hold a cabinet meeting to discuss the economic situation in the country after Fitch and S&P Global Ratings last week downgraded South Africa to "junk", citing Gordhan's dismissal as one reason.
The president would later take part in his 75th birthday celebrations at a public venue in the township of Soweto, near the commercial hub of Johannesburg.
"Working together we will find solutions," Zuma said in the statement issued by the president's office. (Additional reporting by James Macharia and Nqobile Dludla in Johannesburg; Writing by James Macharia; Editing by Toby Chopra)