Czech police on Tuesday said they had arrested a suspect wanted by the FBI and Europol believed to be one of the world's "main distributors of homosexual child abuse images".
The US intelligence agency had been monitoring the activities of the dual US-Czech national for nearly 10 years when it managed to identify him thanks to a Europol-led joint international operation, Czech police said.
The detainee, whose identity was not made public, "mainly distributed content created by others and gave advice about ways to sexually abuse underage boys or to distribute child sexual abuse content on the dark web", law enforcement said in a statement.
"Investigators in Prague managed to access a considerable quantity of data -- which was originally encrypted and secure," it added.
Due to the scope of the alleged wrongdoing, police described the Czech-American man as one of the three main distributors of child sexual abuse images in the world.
The suspect was caught in February and placed in pre-trial detention, police spokeswoman Kristyna Zelinkova told AFP. He faces up to eight years behind bars.
The announcement by Czech police came as Germany also reported it had detained six Germans linked to a dark web platform used to share child sex abuse content, as part of nationwide raids that led to the capture of huge amounts of material.
Zelinkova said the two cases were not related.
The suspects detained in Germany -- men aged 43 to 69 -- were accused of being the "leading figures behind the dark web platform", police in the North Rhine-Westphalia region said in a statement.