JOHANNESBURG—South Africa's African National Congress has won a commanding victory in general elections, partial results showed Friday, putting President Jacob Zuma on the path to another five-year term in office and extending the party's unbroken string of post-apartheid election victories.
With the results from 97% of all polling stations tabulated, the ruling party led with 62% of the vote, down slightly from the results of 2009 elections. The Democratic Alliance was winning 22% of the vote, gaining a few percentage points from the last election. The Economic Freedom Fighters, led by the expelled ANC member Julius Malema, garnered 6%.
The ANC's emphatic win was its fifth consecutive victory in general elections since Nelson Mandela brought the former liberation movement to power in South Africa's first democratic vote 20 years ago.
This election saw it triumph in all but one of South Africa's nine provinces, despite corruption allegations against Mr. Zuma and high unemployment and gaping income inequality, which has fueled sometimes violent labor strikes.
Opposition parties, however, were unable to significantly capitalize on the ruling party's mishaps and widely perceived ineffectiveness.
Mr. Zuma's declared wish for a second—and under South Africa's constitution final—term in office is expected to be unopposed when the National Assembly with its newly elected ANC majority convenes on May 21 and votes for president.
Although a team of election observers representing the African Union and led by Ghana's former president, John Kofuor, declared Wednesday's election "free, fair, transparent and credible," allegations of voting irregularities percolated on Friday.
Images circulated on social media late Thursday showing black plastic bags containing discarded ballots and ballot boxes wedged between shacks in the township of Alexandra. That triggered protests in which 31 people were arrested, police said.
Mr. Malema said the images didn't reflect an isolated episode, and his party lodged a formal complaint with the independent Electoral Commission of South Africa, which is overseeing the vote count.
"There are many incidents of lost ballots, and ballots found in bins" around Gauteng province, Mr. Malema said. Gauteng is the hub of South Africa's economy and the location of its largest city, Johannesburg.
Gordee Godrich, an EFF campaign organizer, said the purported vote tampering was "well-planned, in the towers of Luthuli House," referring to the ANC's headquarters in downtown Johannesburg.
Mr. Godrich said the EFF would abide by whatever ruling the electoral commission reaches before announcing the final election results on Saturday.
"We have committed ourselves to a peaceful political process," he said. "We don't want to become like other countries that go to war just because of elections."
The main opposition party, the Democratic Alliance, said the castoff ballots represented more benign factors. It said an audit by the electoral commission of the ballots pictured in the photographs indicated that the votes had been counted.
Party leader Helen Zille said the alliance didn't suspect vote fraud. Another official in her party, Jonathan Moakes, said incompetence at the polling stations was the likely reason for the discarded ballots.
Mr. Moakes said he believed the ballots pictured spilling out of black trash bags had literally fallen off government trucks after being counted.
"There appears to have been a wide range of inefficiencies and problems, but I wouldn't go as far to say there were irregularities," he said, adding that the party was still waiting for a full explanation from the electoral commission, which said it was investigating all allegations of voting irregularities.