A former Australian childcare worker has been charged with more than 1,600 offences after allegedly sexually abusing 91 children, filming it, then distributing it online.

Police allege the man preyed on young girls over a 15-year period at a dozen centres in Australia and abroad.

He was arrested in August 2022, but it has taken police a year to investigate and identify alleged victims.

Authorities say it is one of the most “horrific” cases they have ever seen.

The 45-year-old man is facing 246 counts of rape and 673 counts of indecent assault against children – many of them in aggravated circumstances.

The charges carry a maximum sentence of life imprisonment.

He also faces hundreds of charges for filming and distributing child abuse material. Police allege he recorded all of his abuse, and say they found 4000 images and videos on his electronic devices.

The offending allegedly occurred in 10 childcare centres in Queensland, and one each in New South Wales and an unnamed overseas country. The man worked at other childcare centres, but the Australian Federal Police (AFP) says it is “highly confident” he did not offend at those centres.

Speaking to media on Tuesday, AFP Commissioner Justine Gough said the case would be “deeply distressing” for the community.

“It’s beyond the realms of anyone’s imagination, what this person did to these children. You try not to be shocked after a long period of time in the police… but this is a horrific case,” she said.

The 87 Australian children who were allegedly abused – some of whom are now adults – have been identified and their families contacted.

Australian authorities are now working with their international counterparts to contact the other four alleged victims.

Investigators say they caught the man after they were able to identify the background appearing in child abuse material as one of the childcare centres he worked at.

The AFP executed a search warrant at the Brisbane centre on 20 August 2022, before also searching the man’s Gold Coast home and seizing electronic devices allegedly containing child abuse material he had created.

He had been reported to police in Queensland twice before, in 2021 and 2022, but investigators had found insufficient evidence to act, police say.

The man – who is yet to be named – is next due to appear in Brisbane Magistrates Court on 21 August.