A van filled with gas cylinders has exploded outside the head office of a Christian lobbying group in Australia's capital Canberra.

The driver suffered serious burns after the explosion which burnt-out the vehicle and damaged the office which was empty at the time.

Police said the 35-year-old man appeared to have ignited the gas cylinders within the vehicle.

Australian Capital Territory police commander Mark Walters said the motive was unclear but it did not appear to be "politically, religiously or ideologically" motivated.

"We do not believe there is any threat to the community as a result of this particular incident," he added.

Australian Christian Lobby's (ACL) managing director Lyle Shelton tweeted pictures of the vehicle and said he was "shocked that this could happen in Australia".

Speaking outside the headquarters, Mr Shelton later said his group had received anonymous threats over the past year .

The ACL is known for its opposition to same-sex marriage, abortion and equality for transgender students among others.

"I am quite shocked actually, this is a scene of absolute devastation... This is not the Australia that I grew up in," Mr Shelton said.

Justice minister Michael Keenan confirmed the incident was not being treated as a terror attack.

Investigations are continuing.