22/12/2016 7:32 AM AEDT | Updated 22/12/2016 10:51 AM AEDT

'Car Bomb' Targets Christian Lobby In Canberra

The leading same sex marriage opponent says the van explosion is an “attack on free speech.”

CANBERRA – One of the most vocal opponents of same sex marriage in Australia, Christian Lobby head Lyle Shelton, is reeling after a large overnight explosion outside his Canberra office he is referring to as a "car bombing".

ACT police are investigating the fiery destruction of a van containing gas cylinders after it was allegedly rammed into the front door of the headquarters of the Australian Christian Lobby (ACL) shortly after 11.30pm.

ACT Police have told The Huffington Post Australia the alleged driver is receiving medical treatment in Canberra Hospital for injuries and no arrests have been made.

No ACL staff were in the building at the time, but they are said to be in shock.

"Makes me feel devastated," the ACL's managing director Lyle Shelton said on arriving at the scene. "It is very emotional to see this sort of thing. I have worked in this building for eight or nine years."

Andrew Meares/Fairfax
The melted front door of the Australian Christian Lobby in Canberra

Daylight has revealed the damage to be extensive, with the glass door melted, windows blown out across the two-storey building and the area scorched. The roof is reportedly unstable.

Investigating police have removed the van, but the remnants of melted tyres can clearly be seen in the driveway.

ACT Police have described the fiery incident as a "collision," but Shelton has stated the incident was a "car bombing" or a "detonation," and also an "attack on free speech".

"I am sure it is a message to intimidate us and cause us to be silent in the public square," he told reporters on the scene.

"And that is something that we are not prepared to do."

The ACL describes itself as "bringing Christian values to politics" and is a vocal opponent of marriage equality, safe schools program, abortion and euthanasia.

He said the Christian Lobby had received multiple death threats and threats of violence through out the year "mainly from anonymous callers" but also allegedly by some "well known gay activists."

Shelton said it was too early to state what caused the incident, but he has ideas.

"I stress I don't know the motivation of last night's attack," he said. "But in the context of the threats we have already received it is deeply unsettling."

"I am very concerned when members of parliament, particularly on the extreme left, refer to us in the parliament as 'hate groups', as 'bigots.'"

"I am sure that does not help the situation if there are people out there who are a bit unhinged."

"That sort of rhetoric does not help."

Nationals MP George Christensen has offered his support, tweeting to Shelton, "I hope you're all ok. If this indeed a politically motivated attack it is disgraceful & should be denounced".

Shelton said he was shocked such an incident could happen in Australia and "all prayers were appreciated".

He said he had "no malice" for the man receiving care in hospital and also offered him "hopes and prayers."