Ananova:

Thieves who stole a Claude Monet painting worth £715,000 from a national museum made a clean getaway after replacing the masterpiece with a cheap forgery.

Visitors and staff at the Polish National Musuem had stared admiringly at the classic "Monet" masterstrokes on the painting - until someone looked more closely, noticed it was a fake and that the genuine article was missing.

Police don't know exactly when the switch was made.

"The original painting has been cut from its frame and a false one put in instead," police spokesman Andrzej Borowiak told the Polish PAP news agency.

The painting, Pourville Beach, was created by the French master in 1882.

Polish police have alerted all border crossings about the theft from the museum in Poznan.

A spokesman for London auctioneers Sotheby's told Ananova: "It is most unusual, the first time I've heard anything like this before. I've never heard of anyone going to the trouble to replace a stolen item with a forgery. Thieves normally just cut the painting from the frame, roll it up and make off."