A fire at one of Russia's biggest libraries has destroyed more than 14 million books.

More than 200 firefighters took 17 hours to bring the fire at The Academic Institute of Scientific Information on Social Sciences (INION), in Moscow under control.

Yuri Pivovarov, the institute's director, which branded the fire a "disaster" said the extent of the damage remained unclear.

It is believed more than 21,500sq ft of the fire has destroyed which started on the building's third floor at around 10pm local (7pm GMT) on Friday and prompted the roof to cave in.

A police official told RIA Novosti news agency "a short circuit in the electrical system is currently being regarded as a primary lead" in the cause of the fire.

INION is home to the biggest collection of rare medieval Slavic books in Russia, which is said to be unaffected.

The institute was founded in 1918 and holds documents from the League of Nations, UNESCO, and early parliamentary reports dating back as far as 1789.