A man alleged to have sexually abused 30 children over three decades while providing schooling and accommodation is before the courts following a joint police investigation.

The 65-year-old South Australian man is alleged to have travelled multiple times to the Northern Territory, returning with children who he then abused.

The man was arrested and charged with two child sex offences in 2023.

Know the news with the 7NEWS app: Download today

Further charges have now been laid — totalling 44 alleged sex offences against 30 children from 1990 to 2023 — after an ongoing joint SA and NT police investigation.

The charges include sexual abuse of a child, unlawful sexual intercourse, indecent and aggravated indecent assault and possessing child exploitation material.

The man appeared in SA District Court on Wednesday.

SA Police acting Assistant Commissioner of Crime Service Catherine Hilliard said it was a “complex and incredibly confronting investigation”.

“The privacy and safety of the victims remains our number one priority,” Hilliard said.

“We have been providing updates, along with support, to everyone effected.”

Northern Territory Police Force Assistant Commissioner Michael White said the alleged offending was “abhorrent” and its scale disturbing.

He assured the community it was believed the alleged offender acted alone.

The two commissioners urged anyone with further information to contact police.

If you or someone you know is impacted by sexual assault, domestic or family violence, call 1800RESPECT on 1800 737 732 or visit 1800RESPECT.org.au.

In an emergency, call 000.