A New Zealand police investigation led to the arrest of a couple in the Philippines after they were caught in the act of live-streaming the sexual abuse of their children.

Following the discovery of "disturbing content" on a Kiwi man's computer in September police here tipped off their counterparts in Iligan City who then organised a raid of the couple's home and caught them during a live-stream involving their children aged four, five and seven.

The couple are now facing charges of human trafficking, child pornography, child abuse and cybercrime.

The woman is pregnant with her fourth child and police say if they had not been caught the new baby could have been subjected to sexual abuse.

The raid and rescue of the children was down to the work of the specialist police team OCEANZ - Online Child Exploitation Across New Zealand.

OCEANZ works to save children as part of a Virtual Global Taskforce (VGT) focused on child exploitation.

Detective Senior Sergeant John Michael said the arrest was "very exciting" for his team.

"We're really happy," he said.

"This is the best job in police, our investigators regularly walk home from work knowing that, for the work we have done, children have been rescued.

"That's the most satisfying feeling out."

Michael said live-streaming of the sexual abuse of children was increasing at an alarming rate.

This was the first time OCEANZ had worked alongside the Filipino authorities - but they had worked with other Asian and European countries to rescue abused children, including the Ukraine most recently.

"In some cases the organisers are not related to the children - they are recruited from their families under false promises like domestic work," he explained.

"Or they offer homeless children or street kids a place to stay or food, and then involve them in this criminal activity.

"On the other hand there are parents and caregivers of children that unfortunately see this as legitimate income."

Michael said most of this kind of sex trafficking was driven by poverty.

"These are families willing to send their children off for a better life," he said.

"But they get duped into criminal groups.

"With traditional sex tourism you get middle age western men who plan to have sex with children - so this live streaming is seen by some people as not being as bad.

"There is no one involved in the abuse of the children so it's not as bad and a lot of money can be made."

Michael said the live-streaming was predominantly coming out of the Philippines.

He could not speak about the specifics of the New Zealand man's case as it was before the courts, and authorities overseas were still investigating.

But he revealed that the man was stopped by Customs after information sent to the New Zealand police by the FBI.

The man was arrested and is facing charges relating to sex trafficking and child exploitation.

"From that, we unravelled further information that led us to suspect three young children in the Philippines were being abused and live streamed," Michael said.

OCEANZ staff worked closely with the Philippines National Bureau of Investigation's anti-trafficking division to located the family.

The NBI was supported in the raid by the International Justice Mission.

"They were in the middle of live streaming," Michael said.

"It was really horrendous."

The NBI division chief Janet Francisco said: "I do not understand why the parent can commit abuse, sell their own children."

Michael said OCEANZ staff were committed to stamping out child sex trafficking, and he had a stern message for anyone in New Zealand that was involved - or considering it.

"This isn't a crime trend anymore, it's an established crime type," he said.

"It will keep going, there's money to be made.

"We'll keep doing our job… if you're going to engage in that kind of behaviour, if you think you can sit there and get away with it, you've got another thing coming.

"We'll catch up with you eventually."