TURIN (AFP).- The only existing self-portrait by Italian master Leonardo da Vinci is making a rare appearance in a new exhibition in Turin in northern Italy, organisers said Tuesday.

The fragile and fading chalk sketch, which has only been put on show for the public three times in the last century, is being displayed for two and a half months as part of "Leonardo and the treasures of the king", which opened on Thursday.

The exhibition is made up of some 80 masterpieces conserved in the Royal Library in Turin, which was founded in 1839 by Charles Albert -- then King of Piedmont and Sardinia -- and is now part of a UNESCO world heritage site.

"The library contains 4,500 manuscripts, 1,500 parchments and over 3,000 drawings by the greatest artists," Maurizio Cibrario, head of Consulta, an association which restores and promotes Turin's cultural heritage, told AFP.

The exhibition, which runs until January 15, includes works by Renaissance artist Raphael, Baroque painter Carrache, Dutch master Rembrandt and Flemish Baroque portraitist Anthony van Dyck, as well as manuscripts and nautical manuscripts.

Visitors must reserve tickets, with admission limited to 25 people every half hour.