South Africans are voting on Wednesday to elect a new parliament, in what could be a pivotal election.
The elections are seen as the most significant since freedom fighter and later president Nelson Mandela led the country to democracy in 1994.
The African National Congress (ANC), which has ruled South Africa continuously since the end of apartheid, is in danger of losing its absolute majority for the first time since then.
Opinion polls suggest the ANC will fall below 50% and will have to form a coalition.
President Cyril Ramaphosa voted in Soweto, a township on the outskirts of Johannesburg. "I have no doubt in my heart that the people will give the African National Congress another chance," he said.
"Each and every vote counts today," said former president Kgalema Mothlanthe.
Elsewhere, lengthy queues formed outside polling stations in many parts of the country, indicating a high turnout, according to the National Electoral Commission.
Despite short delays at some polling stations and isolated protests and attempts to obstruct the work of electoral authority staff, the election was largely peaceful and went smoothly, the authority said.
The biggest competition for the ANC is the liberal Democratic Alliance (DA), which already governs the Western Cape at national level.
The Marxist-influenced Economic Freedom Fighters (EFF) party, led by the former chairman of the ANC youth organization, Julius Malema, is also winning votes from the ANC.
A further party and a newcomer is also fast gaining popularity, namely the Umkhonto we Sizwe (MK) party led by former president Jacob Zuma.
Results are expected on Sunday.
The reason for the ANC's foreseeably poorer performance in the country of 61 million inhabitants is a weak government record.
South Africa is struggling with a weakening economy, high unemployment and poverty, ailing state-owned companies, regular power cuts and failures in the water supply, a crumbling health care system as well as high crime rates and a dysfunctional criminal justice system.
Members of 52 parties are competing for the 400 seats in parliament.
New provincial governments will also be elected. Of the 40.1 million eligible voters, 27.4 million, or around 68% have registered to cast their vote.
Polls opened at 7 am (0500 GMT) and are closing at 9 pm. The newly elected parliament must then form a government and elect a president within 14 days.
Under the constitution, the president is appointed by parliament and not directly elected.
The elections are likely to have a wider impact as South Africa is the continent's largest economy and plays a key political role.
Known as the "gateway to Africa," it is seen as providing access to a continent that is of growing global importance thanks to rich raw materials deposits needed for energy transitions worldwide.
While South Africa maintains good relations with Western countries, the government also has close ties with Russia and China.
South Africa is also taking a strong pro-Palestinian stance in the Gaza war, having filed a lawsuit against Israel at the International Court of Justice for genocide in the Gaza Strip.
