An Australian man has been sentenced to 129 years in a Philippine jail as part of a child sexual abuse case involving victims as young as 18 months, a prosecutor said Wednesday.

It was the second conviction for Peter Gerard Scully, who is already serving a life sentence for an initial batch of charges involving the rape and trafficking of girls.

The Philippines has become a global hotspot for child sex exploitation, helped by poverty, English fluency and high internet connectivity in the country, experts warn.

"I hope this sends a very strong message to all abusers, all human traffickers, that crime really does not pay," Merlynn Barola-Uy, a regional prosecutor in the southern city of Cagayan de Oro, told AFP.

A Cagayan de Oro court handed down the sentence on November 3 after Scully and his three co-accused entered into a plea bargaining agreement.

They had been charged with 60 offences, including trafficking, child pornography, child abuse and rape.

Scully's girlfriend, Lovely Margallo, was sentenced to 126 years in jail. Two others were given sentences of more than nine years.

Victims and their families have accepted the terms of the agreement and consider it a "sweet victory", according to a statement posted on the regional prosecution office's Facebook page.

"They all want to put closure to this dark phase of their lives and move on," the statement reads.

Victims included an 18-month-old baby girl and a child whose body was found buried under the floor of a house rented by Scully, Barola-Uy said.

"This is a big victory, not only for us prosecutors in the Department of Justice, but more importantly this is a big victory for the victim-survivors," she said.

Scully was arrested in 2015 in Malaybalay, another southern Philippine city, after fleeing from Australia in 2011.

He had come to the Philippines to escape fraud charges in his home country.