Europol said 25 WhatsApp groups, formed by invitation only, are being investigated for links to an online paedophile ring

Police have arrested 39 suspects in over a dozen countries across Europe and Latin America after busting an online paedophile ring that used the WhatsApp chat service to share images of child sex abuse, officials said Tuesday.

In coordinated swoops late last month, local and international authorities searched houses and seized hundreds of devices containing child sexual exploitation material in South and Central America as well as Germany, Italy and Spain, Europe's policing agency Europol said in a statement.

"These offenders are pushing the boundaries of modern technology to try to avoid being caught by law enforcement," Europol's director Rob Wainwright said.

Dubbed "Operation Tantalio", the investigation was sparked in mid-2016 by the Spanish police's High-Tech Crime Unit focusing on the Tor encryption network, used by criminals to mask their identities.

"Prompted by clear evidence of prolific sharing of indecent images, the Spanish investigators revealed links diverting users to private groups on WhatsApp," Europol said.

A total of 25 groups, formed by invitation only, are currently being investigated, according to Europol. Hundreds of devices containing pornographic material have been seized, it added.

Spanish police said the photos and videos that were seized showed "humiliating treatment" and "excessive brutality" involving children from babies to children up to eight years old.

Europol and international law enforcement agency Interpol, which also took part in the investigation, said 38 suspects had been arrested but Spanish police said "so far" 39 people had been held, including 17 in Spain.

The other arrests took place in Bolivia, Chile, Costa Rica, Colombia, El Salvador, Germany, Italy, Paraguay and Portugal.

Spanish police said they found handwritten material at a house they searched in Lugo in the north of the country listing the names, ages, and places where encounters with minors took place. Some of them dated back 20 years.

"We need to continue to combine our joint resources and skills to tackle this threat to our children and bring these offenders to justice," Wainwright said.

"Actions like Operation Tantalio send a strong message" that police across the globe will continue to work together to bring to justice those "engaging in or benefitting from the heinous crimes," added Bjorn Sellstrom, Interpol Crimes Against Children operations coordinator.

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© 2017 AFP