I do think that art in general and Chagall in particular must serve dialogue, overture and peace

Yehuda Lancry Israel's UN ambassador

Chagall's oil painting, "Study for Over Vitebsk", was discovered missing from Manhattan's Jewish Museum in June, after a cocktail party for 200 guests.

It appeared at first to be an ordinary art theft - the work is valued at more than $1 million and was on loan from a private collector in Russia.

But then the Jewish Museum received a letter saying the price for the painting's return was peace in the Middle East.

Political art

The letter was postmarked in New York's Bronx and signed by a group called the International Committee for Art and Peace, which is not familiar to the police or the FBI.

It is still not clear if the letter is real or a hoax but it is believed to contain information which could only have come from someone with the painting in their possession.

I like Chagall

Nasser al-Kidwa Palestinian official

For now police are treating the incident as a highly unusual case of art being stolen for political purposes.

Art historians say they can only remember two other similar cases - one a theft by the IRA of works from a private collection in Britain, the other in Norway six years ago, when the famous work "The Scream" by Edvard Munch was stolen from the National Gallery.

Both works were later recovered.