CANBERRA (AFP) - A van laden with gas cylinders has exploded outside the headquarters of an Australian Christian lobby group, but police on Thursday (Dec 22) said the blast was neither politically nor religiously motivated.
Australian Christian Lobby's managing director Lyle Shelton tweeted pictures of the burnt-out white vehicle and said he was "shocked that this could happen in Australia".
He added that the group this year received death threats for taking a stand against same-sex marriage, suggesting the incident could be linked.
But Australian Capital Territory police commander Mark Walters said the motive for the incident, in which only the driver was injured, remained unclear.
"The driver appears to have ignited gas cylinders within the vehicle, causing an explosion which damaged the vehicle and building," he said.
"Police spoke briefly with the man before he continued with treatment. Police were able to establish the man's actions were not politically, religiously or ideologically motivated."
The driver, a 35-year-old Australian, walked to hospital after the blast and was in a critical condition with serious burns. Police plan to speak with him again as soon as they can.
The blast comes days after a truck drove into a Christmas market in Berlin, killing 12 people in an attack claimed by the Islamic State in Iraq and Syria (ISIS) militant group.
Justice Minister Michael Keenan said the Wednesday night collision in Canberra was not being treated as a terror attack.
"At the moment (police) are not treating it as a terrorist incident and there's no ongoing safety issues for the community," he told the Australian Broadcasting Corporation.
The building, which was vacant at the time, suffered damage including broken windows, with oil and debris strewn over the car park.
The ACL lobbies for Christian principles and ethics reforms in parliament, campaigning against gay marriage as well as a school programme that aims to reduce homophobic bullying.
"My team, my staff have had to endure numerous death threats over the course of this year because of our advocacy on something as simple as marriage between a man and a woman," Shelton told reporters.
He said the group was forced to cancel an event at a Sydney hotel in September following threats from same-sex marriage advocates.
"I don't know the motivation of last night's attack but the context of what I see here is in the context of multiple death threats and threats of violence," he said, vowing not to be deterred.
Alex Greenwich, co-chair of advocacy group Australian Marriage Equality, condemned the incident.
"Thoughts and prayers are with everyone at the Australian Christian Lobby, shocking and saddening incident," he tweeted.
Australia's parliament last month rejected a government proposal for a national vote on whether to legalise same-sex marriage.
The Labor opposition said the plebiscite would have sparked harmful debate against the gay and lesbian community and demanded a direct vote in parliament instead.
Currently, same-sex couples can have civil unions or register their relationships in most Australian states, but the government does not consider them married under national law.
Police commander Walters said officers would investigate all previous threats to the Australian Christian Lobby, and reassured the community that "there is no threat to public safety".