Philippines authorities have filed charges of murder and rape against an Australian man arrested over child sexual abuse in the Philippines.

Peter Gerard Scully, who was arrested in the southern Philippines city of Malaybalay last month, is accused of murdering an 11-year-old girl and has also been charged with trafficking, cybercrime and child abuse offences.

• Accused Aust sex abuser investigated for murder

Police allege the 51-year-old sexually abused at least eight girls, including an 18-month-old infant, between 2011 and 2014.

Investigators said he allegedly strangled one of the girls to death, with her skeleton later discovered buried under a house he had rented.

Three Filipinos, including his former partner, and a German national, have also been charged in connection with child abuse and internet pornography.

Australian Federal Police have confirmed a number of officers will travel to the Philippines next week to assist with what has become a major investigation into child sexual abuse.

A complaint filed by Philippines Justice Department investigators with the prosecutors’ office said Scully forced the girls to perform sexual acts in front of a video camera for paying clients overseas.

“Let notice be served to these criminal elements that the days of their child cybersex operations are numbered,” Justice Secretary Leila de Lima said in a statement on the case.

“Wherever these syndicates are, we will hunt them down and we will bring them to justice.”

In the complaint outlining the case against Scully, a 13-year-old girl was quoted as saying that her impoverished family agreed she could do domestic work at his home in 2012.

But she was instead forced to perform sex acts with other girls, and was beaten by Scully’s Filipina girlfriend when she refused, according to the prosecutors’ complaint.

“They told me they had to take pictures of me naked because there was an American who really wanted to see me naked… and because the American will pay a large amount,” the complaint quoted her as saying.

The girl said she fled Scully’s house after she learned he had sold her to a German national who was coming to collect her, the complaint said.

The head of the anti-human trafficking division of the justice department’s investigating arm, Eric Nuqui, said that Scully had been the subject of an international probe after Dutch police found out about his activities.

If convicted, the Australian could face life in prison.

Authorities have warned the Philippines is a major hub of a billion-dollar global child cybersex industry, with operators aided by widespread poverty and legal loopholes that allow them to remain anonymous.

Last year, Ms de Lima said that online child abuse was the leading cyber-related crime in the Philippines, making up 46 per cent of the more than 200 cases being handled by law-enforcement agencies.

ABC/AFP