A three-year international investigation into the online sexual abuse of children has resulted in the arrest of over 150 people, including 16 Canadians, police revealed on Thursday.

Project Mercury is a joint investigation between authorities in Canada, the U.S. and eight European countries, including the U.K., France, and Germany.

Since 2014, some 153 people have been arrested. For those convicted, the sentences have ranged from 30 months to 60 years, with many cases still before the courts.

The youngest victim was a 10-month-old.

"It's important to understand that this is happening to children all over the world," Toronto police Staff Supt. Myron Demkiw said at the press conference on Thursday.

Members from the Toronto police sex crimes unit were joined at police headquarters in downtown Toronto on Thursday by representatives of U.S. Homeland Security Investigations, the U.K.'s National Crime Agency, a Saskatchewan RCMP unit and the Ottawa Police Service.

Staff superintendent Myron demkiw: children are not only being sexually abused. There are permanent recordings. <a href="https://t.co/aEAAVAPSA5">pic.twitter.com/aEAAVAPSA5</a> —@LisaYaxiXing

Suspects used 'various social networking platforms,' say police

Police in Toronto launched an undercover investigation in January 2015, after the National Crime Agency in the U.K. alerted police agencies around the world of an online group "using various social networking platforms" to distribute child abuse material, said Toronto Police Det. Const. Janelle Blackadar.

In July 2015, Toronto police witnessed a live-streaming event in which a six-year-old child was abused while other people from around the world commented and directed the abuser.

Police say within hours the child was rescued and the abuser was caught in Pennsylvania. More than 20 other offenders were arrested, mainly in the U.S. and the U.K.

Toronto Police Det. Const. Janelle Blackadar speaks about Project Mercury on Thursday at Toronto Police Headquarters in Toronto. (Toronto Police Service)

"Unfortunately this was not the first time this happened, but I can tell you it was the last," Blackadar said.

Several other investigations uncovered similar live-streaming events, one in March 2016 when Toronto police discovered a man in Saskatoon, who had drugged an eight-year-old boy and invited others online to virtually take part in the child's abuse.

Again, within hours of the RCMP identifying the suspect, the child was saved.

Toronto police have helped with 16 investigations in Canada, which have resulted in 13 convictions. Seven arrests have been made in Toronto, two in Ottawa, and one each in Belleville, Thunder Bay, Quebec, Edmonton, Newfoundland, New Brunswick and Saskatoon.