CANBERRA, Australia (AP) — Australia's prime minister on Friday urged restraint in the nation's same-sex marriage debate after predecessor Tony Abbott said he was head-butted by a gay rights advocate and sustained a swollen lip.

Abbott said he was attacked in the Tasmania state capital Hobart on Thursday as he walked with a staffer to his hotel after attending an anti-gay marriage luncheon.

Police on Friday charged a 38-year-old Hobart man with assault. The man, who has not been named, was released on bail to appear in court next month, a police statement said. He faces a potential 12-month prison sentence if convicted.

The altercation is one of several allegations of violence and vote-rigging that have marred an ongoing postal ballot on whether Australia should lift its prohibition on gay marriage. Australia and Ireland are the only countries to put the issue to the public to decide.

Abbott remains a government lawmaker and is a vocal advocate for the "no" vote. The two-month voting process began last week.

He reported to police that a man wearing a "vote yes" badge pretended to want to shake hands before clashing heads. The assailant fled after a brief scuffle with the staffer.

"It's a shock to have a fellow Australian seeking to shake your hand turn a handshake into an assault," Abbott said on Friday.

"There is no doubt that there has been some ugliness as part of this debate, but I regret to say that nearly all of it seems to be coming from one side and that is the people who tell us that love is love," he added.

Prime Minister Malcom Turnbull, a gay marriage supporter who replaced Abbott two years ago, said he had urged police to press charges.

"This is a disgraceful incident and I condemn this assault on Tony and any violence coming into our political life is absolutely to be condemned," Turnbull told Radio 3AW.

"Everyone should exercise calm and restraint, and people should recognize that they are not helping their cause by engaging in violent language, abusive language, let alone physically violent conduct ... as Tony suffered from last night," Turnbull added.

Advocates on both sides of the debate have been punished for taking public stances in the campaign.

The Australian Football League headquarters in Melbourne was evacuated by a bomb hoax on Thursday, a day after it removed a "yes" logo from its front door. The logo had been displayed for only a day and football officials had been inundated with complaints from the public for taking a position in the heated debate.

A Presbyterian church minister announced last week that he would refuse to marry a couple in a Ballarat church after the 26-year-old bride-to-be revealed on social media her support for same-sex marriage.

An 18-year-old woman was fired from a Canberra children's party business last weekend because she posted on social media: "It's OK to vote 'no'," a slogan her employer described as "hate speech."

Abbott was prime minister in 2015 when he committed his conservative government to holding a compulsory vote by all adult Australians to decide whether gay marriage should be legal.

He was replaced weeks later by Turnbull, who opposed the public vote but agreed to maintain Abbott's policy in a deal with the powerbrokers who ousted Abbott in an internal leadership ballot.

The Senate refused to fund a compulsory vote, so the government is proceeding with a voluntary postal ballot which critics say is unlikely to accurately reflect public opinion.

Lawmakers would still have to pass a law to allow gay marriage and several have said they would not allow it regardless of public opinion.

Most gay rights advocates had argued against a public vote for fear that it would lead to a bitter public debate. They want lawmakers to decide the issue without consultation with the public.

Successive opinion polls in recent years show that most Australians support marriage equality.

Kevin Rudd, a center-left Labor Party prime minister whom Abbott defeated in elections in 2013, blamed the postal ballot for an assault on his godson Sean Foster, 19, as he campaigned for marriage equality in Brisbane city last week.

"So many warnings to Turnbull about what the postal vote cld unleash. Now my godson Sean has been punched standing up for #MarriageEquality," Rudd tweeted with a photograph showing Foster's bloodied forehead.

Police have charged a 48-year-old man with assaulting Foster.