Hundreds of people were arrested around the world following an investigation into “the largest dark web" child sex abuse marketplace.

Now closed, the website hosted more than 200,000 unique videos showing illegal sex acts committed against children, toddlers and infants, according to an 18-page criminal indictment unsealed in Washington.

That amounts to almost eight terabytes of data containing child sex abuse images, which drove a Bitcoin based marketplace with 7,300 transactions of the cryptocurrency worth more than $730,000 (£569,000).

“You may try to hide behind technology,” Jessie Liu, the US attorney for the District of Columbia said during a press conference. “But, we will find you and arrest you and prosecute you.”

The now-shuttered English website “Welcome to Video” is said to have been started by South Korean national Jong Woo Son, a 23-year-old who is currently serving an 18-month prison term in his home country for charges concerning child sex abuse images.

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It was online from June 2015 until March 2018, when US authorities shut the operation down.

Authorities said that many of the videos hosted on the website were previously unknown to the National Centre for Missing and Exploited Children, a US non-profit set up by congress to search for missing children and combat child exploitation.

“The scale of this crime is eye-popping and sickening,” said John Fort, the chief of IRS criminal investigations.

The website was only run on the dark net, a section of the internet accessible by a Tor browser to hide their identities. It was one of the first to use cryptocurrency Bitcoin to make a profit from children's suffering.

The dark net is set up in order to make tracking online footprints more difficult, and to obscure who is accessing any particular data.

The arrests were made in 38 countries including the UK, Ireland, the US, South Korea, Germany, Spain, Saudi Arabia, the United Arab Emirates, the Czech Republic and Canada.

They were sparked by an investigation by the National Crime Agency (NCA), Britain's answer to the FBI, into one of the UK’s worst ever child sex offenders.

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Seven men have already been convicted in Britain – including 26-year-old Kyle Fox who was jailed for 22 years in March for raping a five-year-old boy and appearing on Welcome To Video sexually abusing a three-year-old girl.

Using "specialist capabilities" investigators said they were able to trace Son and the hundreds of users through their Bitcoin transactions.

The arrests are the result of years hunting by the Nation Crime Agency (NCA), Britain's version of the FBI, which first came across Welcome To Video while investigating geophysicist Dr Matthew Falder.

Falder admitted 137 offences in 2017 including encouraging child rape and sharing images of a newborn baby being abused and is serving 25 years behind bars in the UK.