JOHANNESBURG — In the largest protest in years, tens of thousands of people demonstrated in South Africa’s major cities on Friday to demand the resignation of President Jacob Zuma after his dismissal of a well-respected finance minister intensified concerns about government corruption.
Marches in Cape Town, Durban, Johannesburg and Pretoria brought together a mix of political opponents, civil society leaders and ordinary South Africans, united in their message that Mr. Zuma had lost the moral authority to lead the nation. Supporters of Mr. Zuma and his governing African National Congress held smaller counterprotests in Durban and Johannesburg.
The protests were prompted by Mr. Zuma’s abrupt dismissal of the finance minister, Pravin Gordhan, in a midnight cabinet reshuffle last week. Mr. Gordhan, known for his fiscal prudence and oversight of state enterprises, was regarded as a bulwark against the A.N.C.’s perceived culture of corruption and patronage that Mr. Zuma has come to symbolize.
“One person cannot hold the rest of the country hostage,” Mmusi Maimane, the leader of the main opposition party, the Democratic Alliance, said at a march in central Johannesburg.
“Jacob Zuma is not fit to lead South Africa,” he added.
In response, hundreds of veterans of the A.N.C.’s former military wing, dressed in camouflage and singing revolutionary songs, formed a shield in front of the A.N.C.’s headquarters in Johannesburg. The police fired rubber bullets to disperse A.N.C. supporters who were headed toward Democratic Alliance marchers, and clashes between rival protesters were reported elsewhere in the country.
On Friday, South Africa’s government debt was downgraded to junk status by Fitch Ratings, the second rating agency to take such an action since the dismissal of Mr. Gordhan. Fitch said that “recent political events, including a major cabinet reshuffle, will weaken standards of governance and public finances.”
It was far from clear, however, whether the growing opposition would have any effect on Mr. Zuma’s standing inside the A.N.C. Although Mr. Zuma was initially criticized by some of the party’s top leaders for firing Mr. Gordhan, the A.N.C. this week rallied around the president.
With the party expected to select a new leader at a national conference in December, Mr. Zuma appears to have firmed up his position and influence. His critics in the party were forced to apologize this week. His cabinet is now stacked with loyalists. His new finance minister is a longtime ally who is more likely to give the president and his allies easy access to the state coffers.
Thousands of demonstrators, many with “Save South Africa” banners, gathered in Pretoria to march to Union Buildings, the seat of the presidency, after a court lifted a police ban on the protest late Thursday evening.
“The presidency respects the right of South Africans to protest peacefully,” Mr. Zuma said in a statement about the march in Pretoria, but he has not commented further.
In the Cape Town area, demonstrators formed an intermittent human chain from the Cape Peninsula into the city. Thousands gathered at several spots in the city, including in front of Parliament and City Hall, where Nelson Mandela once addressed huge crowds upon his release from Robben Island.
Matshepo Motsoeneng, 52, came to City Hall with her daughter, Tumi, 25, from their home in Khayelitsha, an impoverished black township.
“Never in my life did I think I’d stand against the A.N.C.,” Ms. Motsoeneng said. “There’s been too much corruption. Today, I’m representing what my parents fought for, taking up their struggle for this country. This is not about race, it’s about stopping corruption in the government.”
Her daughter wore a beret of the Economic Freedom Fighters, a radical opposition party, at what was her first protest.
“I’m expecting to see Zuma leave office today,” she said. “We are graduates, but we don’t get jobs. We’re struggling because of his corruption.”