SYDNEY • Australians have voted overwhelmingly for same-sex marriage, paving the way for legislation by the end of this year and sparking rainbow celebrations yesterday, with people wearing wedding dresses and sequined suits, and declaring that "our love is real".

Australia will become the 26th nation to formalise the unions if the legislation is passed by Parliament, which is expected despite some vocal opposition within the government's conservative right wing.

Thousands of people in a Sydney park broke into a loud cheer, hugged and cried as Australia's chief statistician revealed live on a big screen that 61.6 per cent of voters surveyed favoured marriage equality, with 38.4 per cent against.

Australian Olympic swimmer Ian Thorpe, who came out as gay three years ago, said the result was a huge relief.

"It means that the way you feel for another person, whoever that may be, is equal," he told reporters at the Sydney celebrations.

The voluntary poll is non-binding, but Prime Minister Malcolm Turnbull immediately said he would fulfil a pledge to introduce a Bill in Parliament with the aim of passing laws by Christmas.

Mr Turnbull played down concern of a split in his coalition government over the policy as the conservative faction presses for amendments to protect religious freedoms that discriminate against same-sex couples.

"It is unequivocal, it is overwhelming. They have spoken in their millions and they have voted overwhelmingly yes for marriage equality," the Prime Minister told reporters in Canberra after the survey results were announced. "They voted yes for fairness, yes for commitment, yes for love."

A marriage equality Bill was introduced in Parliament later yesterday.

The result marks a watershed moment for gay rights in Australia, where it was illegal in some states to engage in homosexual activity until 1997. "It's a g'day. Way to go Australia," tweeted US TV host Ellen DeGeneres, who is married to Australian actress Portia de Rossi in the United States.

Almost 80 per cent of eligible voters took part in the survey - a higher turnout than Britain's Brexit vote and Ireland's same-sex marriage referendum.

Irish-born Qantas Airways chief executive Alan Joyce, one of the few openly gay business leaders in Australia, told the Sydney crowd, many of whom sheltered from the sun under rainbow umbrellas, that the result was "an amazing outcome", and urged Mr Turnbull to move quickly on legislation.

Mr Turnbull has been under pressure amid a citizenship crisis that has cost him his deputy and the government's majority in Parliament, and political analysts said the resounding "yes" vote presented him with his first opportunity in months to exert decisive control.

Mr Nick Economou, a political scientist at Monash University, said Mr Turnbull "should feel emboldened by the result, and this is the sort of thing he has been looking for to show some assertive leadership".

The "no" campaign had sought to leverage powerful religious organisations in a survey campaign that was criticised by some in the "yes" camp as divisive and aggressive.

Catholic Archbishop of Sydney Anthony Fisher said he was "deeply disappointed that the likely result will be legislation to further deconstruct marriage and family in Australia".

"No" campaigners congratulated their opponents, but vowed to push for religious protections and exemptions. "We will now do what we can to guard against restrictions on freedom of speech and freedom of religion, to defend parents' rights, and to protect Australian kids from being exposed to radical LGBTIQ sex and gender education," said Mr Lyle Shelton of the Coalition for Marriage.

REUTERS, AGENCE FRANCE-PRESSE