South Australians are likely to have to wait for several days to discover whether Labor or the Liberal Party will form government as vote counting continues in the state's tight election.
Both Labor and Liberal leaders claimed they were confident of forming government, but a hung parliament remained the most likely result, leaving two independents to decide who will govern.
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Labor Party faces a major blow, set to lose power in its last state of South Australia after the Liberals claim victory in Tasmania. Nine News.
Although exit polls showed the vast majority of voters believed the state was about to ditch the 12-year-old Labor Government, Labor was holding on with the support of Greens preferences in many crucial seats, and Liberals were pinning fading hopes on winning several Adelaide metropolitan seats.
Liberal insiders were haunted by the prospect of winning the majority of votes, but being left in Opposition - the same result as the last election in 2010.
Labor has held government in the state for the past 12 years.
Labor Premier Jay Weatherill told supporters late Saturday night the vote was still too early to call, but he was confident of forming a new government.
Opposition leader Steven Marshall hailed the Liberals for increasing their primary and two-party preferred vote, stretching it to 5 percent more than Labor, but said he was disappointed he could not announce he was forming government. He said he believed the Liberal party could still pick up enough seats, but also indicated he would do everything he could to form a minority government if required.
South Australian Liberal Party president, former Howard Government Minister Alexander Downer, said the Liberals had almost always won the two-party preferred vote in state elections, but had regularly failed to pick up enough seats to form government.
He said the key to Saturday's election would be how the votes fell in individual seats - and that was "hugely difficult to know".
Vote counting was not advanced enough to offer a clear picture of the election outcome, but the trend suggested the result would be so close a hung parliament or an unexpected Labor win could be the result.
With about 65 per cent of the vote counted, the Liberals had achieved a two-party swing of about 1.9 per cent, giving it 52.7 per cent of the vote. Labor had 47.3 per cent.
Labor held 26 seats, the Liberals held 18 and three were in the hands of the Independents in the lead-up to polling.
The Labor Party held 11 seats by margins below 5 per cent. The Liberal Party must win an extra six seats to achieve government in its own right.
Mr Marshall would not rule out trying to form a minority government with the support of independents if his party fell short of an outright majority of 24 seats, but said he hoped to win outright.
Mr Marshall was still smarting from delivering a gaffe on Friday, when he called on South Australians to "vote Labor".
Both Mr Weatherill and Mr Marshall were facing their first election as leaders. Mr Weatherill replaced Labor Premier Mike Rann in late 2011, and Mr Marshall, who is in his first term as an MP, has been Liberal leader for only 13 months.
Mr Marshall has focused his attack on the government over debt and deficit, and Mr Weatherill has warned that Mr Marshall would simply "set up a branch office in South Australia for (prime minister) Tony Abbott".