An evangelical church in Australia has been threatened with a petrol fire by gay rights activists after it displayed a billboard saying, 'God designed marriage between a man and a woman'.

Amid voting in what is proving to be a divisive postal referendum on same-sex marriage which concludes on November 7, the Bellbowrie Community Church in Brisbane has been the victim of threats and abuse on social media following the billboard display.

Senior pastor John Gill told the Daily Mail Australia: 'On Facebook, a lot of the stuff has been quite vicious at times. I mean quite physically threatening. That's been scary for some in the church.'

He added: 'One of the comments I saw, for example, was a suggestion that people bring petrol down and set the church on fire.'

Separately, a Brisbane resident, Patrick Wood, argued that the billboard promoting traditional marriage contradicted another billboard which said: 'All people are welcome and respected here.'

He wrote on Facebook: 'Their house, their hypocritical rules. Same sign, same day, opposite sides. I won't forget their marriage equality stance.'

Gill said that he was worried about religious freedom. 'At the moment, we know we have that freedom but certainly down the track, we have serious concerns about whether we'd continue to have that freedom or not,' he said.

Quest Community News quoted Gill as saying that his congregation is free to vote in the plebiscite however they choose. 'As a pastor, it is not my place to tell people how to vote,' he said.

'Many of us have friends and family who are gay, and it is absurd to think we hate them. We love them very much. It is possible to hold different views, yet still love people. So this does not need to be a source of division throughout Australia. We can differ, yet still respect and care for each other and let the voting determine the issue.'

At the weekend, the billboard at the Bellbowrie church was tampered with to say: 'God designed marriage between a man and a man.'

One post on Facebook said: 'Hopefully there are churches in the area that cater to ALL Christians and not just the ones who fit in the narrow minded view of this "Church of God". I'm sure Christ would be very disappointed in your view of Christianity.'

Another woman wrote: 'A closed-minded group which overtly discriminates against members of our valued community and their (very reasonable) quest for marriage equality.'

Cartoons of same sex couples and sailors waving rainbow flags were posted in the comments under unrelated posts by the church, and some users took to posting one star reviews of the church.

All the reviews and comments about the issue later disappeared from the site.

The Daily Mail quoted a teacher from the New South Wales Central Coast, opposed to gay marriage, who said the church billboards were consistent with Christian teachings.

'This is not a contradiction. It is perfectly in order and reflects our Christian ethos: acceptance of individuals regardless while upholding the sanctity of marriage and simultaneously rejecting SSM with its ramifications,' he said.