Protection of journalistic sources is very strong in Sweden.

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The massive release of secret military documents on the Afghan war by WikiLeaks highlights the security challenges of the digital age, when gigabytes of sensitive data can be exposed with a single click.

The websites founder Julian Assange said that Sweden plays a important role in the operation of Wikileaks.

First, the website is hosted in Sweden. Julian Assange also told Swedish Radio News that the organization passes information via Sweden to protect sources.

Sweden has a strong tradition of freedom of speech and freedom of the press. Protection of journalistic sources in Sweden is very strong.

"We use state of the art encryption to bounce stuff around the internet, to hide trails, pass it through legal jurisdictions like Sweden and Belgium, to enact those legal protections," Julian Assange told Swedish Radio in an interview in July.

The Nordic countries top Reporters Without Borders' press freedom index, with Denmark at the head, followed by Finland, Ireland, Norway and Sweden.

The US Army formally opened a criminal investigation Tuesday into the leak of tens of thousands of classified military documents on the Afghan war, the Pentagon said.