Dozens of previously unseen artworks were among the hundreds of Nazi-looted pieces discovered in Germany, it has been revealed.

German authorities displayed paintings by Marc Chagall, Henri Matisse and other renowned artists during a press conference in Munich on Tuesday morning.

It was the first time pieces from the 1,400-strong hoard had been shown. Work by artists including Picasso and Canaletto was also recovered.

Efforts are still being made to identify the rightful owners of the art, 18 months after the collection was discovered in a flat in the city. Many of the items were stolen from Jewish families in Europe before and during the Holocaust, German authorities confirmed.

The value of the artwork is thought to be close to £1 billion. Most of the pieces are in good condition, despite being stored in the property for more than half a century.

Restitution experts have criticised investigators for waiting so long since the hoard was uncovered to make it public.

A Claims Conference spokesman demanded that works taken from Jews should be immediately returned to Shoah survivors.

The advanced age of the remaining survivors meant authorities should be working as fast as possible to identify the correct owners, experts said.

Prosecutors in Augsburg, Bavaria, said the collection included 121 framed pieces and 1,258 unframed works. They warned that the legal situation surrounding the works was "extremely complex" and that it was unclear whether flat-owner Cornelius Gurlitt had committed any offences.

It is not known where Mr Gurlitt is now living. His father, Hildebrand, was an art dealer in Munich and was hired by the Nazis to collect artwork regarded as "degenerate" by the Third Reich.