PRETORIA, South Africa — Allegations of an unfair election aired for the first time here late Thursday, when sacks of ballots — mostly for the opposition Democratic Alliance — were found in garbage bags in the key province of Gauteng.
Nearly one-third of South Africa’s 52 million people live in Gauteng, which encompasses the capital, Pretoria; the commercial hub, Johannesburg; and some of the world’s richest gold mines.
Ballot boxes were found hidden between shacks in some of the province’s poorest shanty towns, along with the trash bags of voting forms.
The discovery of so many discarded ballots in the province casts doubt on the election’s fairness, said Mmusi Maimane, the Democratic Alliance candidate for premier in Gauteng.
“It is clear there has been interference,” Mr. Maimane told journalists at the counting center in Pretoria. “We are bitterly concerned about this.”
The ruling African National Congress did not provide an immediate response to the allegation.
Some of the dumped votes have since been counted, and the Independent Electoral Commission has pledged to investigate the matter.
Millions of South Africans voted Wednesday in the fifth set of parliamentary and provincial elections since the end of white-minority rule in 1994.
With most of the counting completed Thursday, the African National Congress had won about 63 percent of the vote, down from the 65.9 percent it won five years ago.
The results give the African National Congress its fifth consecutive parliamentary win and President Jacob Zuma a second five-year term — his last under the constitution.
The Democratic Alliance had won about 22 percent of the vote, and the Economic Freedom Fighters, a new party that wants to nationalize banks and mines, was third, with 5.5 percent.
Election officials estimated that 73 percent of the nation’s 25 million registered voters turned out to cast ballots.
More than 30 parties competed in the parliamentary elections. Under South Africa’s system of proportional representation, the National Assembly’s 400 seats will be divvied up among parties based on their vote tallies.
The Democratic Alliance maintained its dominance in Western Cape province, and displaced other parties to become official opposition in all but one of the nation’s remaining eight provinces.
Home to more than 6 million people, Western Cape province re-elected Democratic Alliance leader Helen Zille as premier.
Ms. Zille, whose grandparents fled Nazi Germany, speaks six languages including English, Afrikaans, Hebrew and Xhosa, the native language of former President Nelson Mandela.
The Economic Freedom Fighters is led by radical newcomer Julius Malema, who previously had run the African National Congress’ youth wing but was expelled from the party for misconduct.
Opposition groups including the Democratic Alliance, the Economic Freedom Fighters and the Inkatha Freedom Party — led by 85-year-old Prince Mangosuthu Buthelezi, who has been in politics since 1953 — have vowed to join forces and uncover the truth behind the trashed votes and dumped ballot boxes.
Opinion polls had predicted an African National Congress loss in Gauteng, and the ruling party appeared set to achieve victory there by only a few percentage points.
Mr. Maimane said for this reason it is vital to find out whether there had been any kind of interference.
“In Gauteng,” he said, “it really could affect the result.”
The Democratic Alliance had accused the African National Congress of jeopardizing its campaign in April, when state-run television banned one of Mr. Maimane’s ads, which were aired only after he had gone to court.
• This article is based in part on wire service reports.
Please read our comment policy before commenting.