JOHANNESBURG (Reuters) - South Africans started voting on Wednesday in an election that could mark a big political shift if the governing African National Congress party loses its majority as opinion polls suggest.

Voters are electing nine provincial legislatures and a new national parliament, which will then choose the country's next president.

If the ANC gets less than 50% of the national vote it will have to seek one or more coalition partners to govern the country, the first such alliance in the 30 years since it swept to power with Nelson Mandela as its leader at the end of apartheid.

Voting stations opened at 0500 GMT and will close at 1900 GMT, with more than 27 million people registered to vote out of a population of roughly 62 million.

South Africa's electoral commission is expected to start releasing partial results within hours of voting stations closing. The commission has seven days to announce final results.

(Reporting by Johannesburg bureau; Writing by Alexander Winning; Editing by Estelle Shirbon)