Police have launched investigations into three arson attacks on churches linked to paedophile priests in Melbourne.

A fire at St Mary's Catholic Church in Dandenong began early on Wednesday morning, causing extensive damage thought to cost around $250,000. The blaze is believed to have begun in two separate places in the church; one in a storage room and another at the alter. The parish is linked to Kevin O'Donnell, a priest who was convicted in 1995 of indecently assaulting 12 children aged between eight and 15-years-old.

O'Donnell served 15 moths in jail before being freed. He died in 1997.

Police are also investigating two earlier attacks on churches in Melbourne. On Monday, a fire almost destroyed St James' church in Brighton, while a separate fire at St Mary's church in St Kilda also caused minor damage.

These two churches are among those served by British priest Ronald Dennis Pickering, who has been accused of sexually abusing several boys across Melbourne between 1960 and the early 1990s. He fled to Margate in the UK in 1993 and the archdiocese admitted in 2002 that he was an offender. Compensation was paid out to his victims, but Pickering died in 2012, never having been charged.

According to local news, Detective Senior Constable Nic Hayes told reporters that the fires were being investigated separately, though there has been speculation that they may be linked to victims of priest abuse.

Chris McIsaac, the founder of Broken Rites - a group that helps victims of church-related abuse - said it is possible.

"It's tragic the church hasn't dealt with this," she told The Age Victoria.

"They've kept this at bay for as long as possible, and paid victims as little as possible, that it would not be surprising if someone has taken it to this."

One of Pickering's alleged victims criticised the church for not bringing the priest to justice while he was alive, and for not offering enough support to those who claim they were abused.

"If a victim is lighting these fires, it's a symptom of anger. But you certainly don't want to encourage this as a way of dealing with anger," he said.

However, regional Bishop for the South, Peter Elliot, told Fairfax Radio that he thought the arson was the work of "a very disturbed" person. "We've had phases of attacks on churches," he said.

"If you go back about 15 years ago there was a spate of them in the Malvern, Camberwell area and then we had the case of the beautiful church at Chelsea nine years ago. So I would suggest it rests in a very disturbed mind of some arsonist who likes burning churches."

Father Declan O'Brien of St Mary's Catholic Church has expressed his sadness at the damage caused. "I'm trying my best to hold onto the Christian principle of forgiveness and at the moment as a human being it's very hard to do that," he said, according to ABC news in Australia.

"I can't understand the motivation of wanting to burn a place of worship... I can understand people being angry, I just don't get why even if they're angry it's justifiable that you'd attack a church building.

"I just can't comprehend that right now, I really, really can't."