Moscow: A fire that ripped through one of Russia's largest university libraries is believed to have damaged over one million historic documents, with some describing the fire as a cultural ‘Chernobyl’.

The blaze, which started Friday and was still not completely out on Saturday evening, ravaged 2,000 square metres of the Institute of Scientific Information on Social Sciences (INION), which was created in 1918 and holds 10 million documents with some dating back to the 16th century.

"It's a major loss for science. This is the largest collection of its kind in the world, probably equivalent to the (United States) Library of Congress," Vladimir Fortov, president of the Russian Academy of Sciences was quoted as saying by Russia press agencies.

"One can find documents there that are impossible to find elsewhere, all the social sciences use this library. What has happened here is reminiscent of Chernobyl," he said referring to the 1986 nuclear catastrophe.

Fortov said about 15 percent of the collection had been damaged at the library, which includes one of the world's richest collections of Slavic language works, but also documents from Britain, Italy and the US.

The fire broke on Friday evening on the library's second floor and continued burning all day Saturday despite 200 firefighters efforts to douse the blaze.

Library authorities initially said the documents were not in danger, but once the fire caused 1,000 square metres of the roof to collapse they were less certain about the risk to the collection.

A rescue service source told state-owned Russian press agency Ria-Novosti it was impossible to remove the books due to the intense heat in the building.