Four children being exploited to produce pornography in the US were rescued as a result of the police crackdown in Victoria.

A four-week operation uncovered about 25,000 images and led to 21 arrests.

The investigation, by Victoria Police’s Taskforce Astraea and the Australian Federal Police’s Child Protection Operations, was held in the lead-up to National Child Protection Week, which started on Monday.

Assistant Commissioner Steve Fontana said four US children were rescued after images were found on computers seized in Victoria that showed them being exploited. 

The images were traced back to the houses of the children.

He said a Victorian man who had been grooming a 10-year-old from Western Australia for sex had been arrested, and five men had also been arrested after approaching police who were posing as children online.

Twenty Victorian men and one Tasmanian man, aged from 18 to 72, were charged with offences, including manufacturing child pornography and procuring a minor for sexual purposes.

Other charges included grooming a child under 16 for sexual purposes, using a carriage service for child abuse material and possessing child pornography. The Kangaroo Flat man was charged with possessing child pornography and accessing or making available child pornography.

He will face court at a later date.

AFP Commander Scott Lee said it was vital that anyone who suspected child abuse was occurring contacted Crime Stoppers and he urged parents to remain vigilant about what their children were doing online.