A van containing gas cylinders has exploded at a Christian lobby group's office in Canberra, Australia, on Wednesday evening.

The van exploded after ramming into the Australian Christian Lobby office. It is thought to have been packed with gas cannisters.

Lyle Shelton, the organisation's managing director, tweeted that all the staff were safe.

"Police contacted me and told me that someone has driven a white van into the car park of our office and it has been loaded with gas cylinders and then it has been detonated," said Shelton, according to Sydney's Daily Telegraph.

"We have had the normal trolls on social media and even had death threats sent to our Canberra office over the year but I am very concerned someone would do this," Shelton said.

"It is a relief the building was unoccupied at the time and we are all very thankful our staff are all safe.

"Obviously this is very unsettling to us but also to anyone in Australia, for this to happen in Canberra, our nation's capital is very disappointing.

"It is something I thought would never happen here, I can't believe it."

The group have been heavily involved in the campaign against same-sex marriage in Australia.

A police investigation has been launched. "Investigations into a vehicle fire at the Australian Christian Lobby and no one was injured inside the building," a spokesman confirmed.