The website of one the Nazis' biggest former concentration camps was hacked with images of child pornography on Friday, the 70th anniversary of the end of World War II, officials said.

Austrian Interior Minister Johanna Mikl-Leitner said the hacking of the website of Mauthausen near Linz in northern Austria was a "criminal, sick attack and deeply abhorrent".

"Interior ministry experts are helping the private operator of the website as we speak to get the site back up as soon as possible. At the same time an investigation is under way," she said.

Mauthausen in Hitler's native Austria was the Nazis' only category III camp, created for "incorrigible political enemies of the Third Reich" and incorporating a vast network of 49 subcamps.

Some 200,000 prisoners from all over Europe and the Soviet Union passed through. Half of them died -- beaten, gassed, starved, shot or worked to death in granite quarries and armaments factories.

"This wasn't a straightforward extermination camp. Its slogan was 'annihilation through labour'," tour guide Casimir Paltinger told AFP in a recent visit ahead of the 70th anniversary of its liberation on 5 May 1945 by US troops.