Armed robbers stole works by Cezanne, Degas, Monet and Van Gogh valued at more than $163 million from a Zurich museum, in Switzerland's biggest art heist and the second theft of paintings in the country in less than a week.

Three armed robbers wearing ski masks took the impressionist and post-impressionist paintings from the E.G. Buehrle Collection in Zurich's Eighth District in an afternoon raid yesterday, 30 minutes before it closed, police said today. They described the attack as "spectacular."

"On the open market, these pictures are unsellable," Lukas Gloor, director of the museum, said at a news conference today. Marco Cortesi, a Zurich police spokesman, confirmed the incident was the "biggest-ever art robbery" in Switzerland.

The U.S. Federal Bureau of Investigation lists Iraqi looted and stolen artifacts on its Web site as the largest-ever art crime, without giving a value. Art looted by the Nazis during World War Two is regarded as war crime rather than theft. The biggest heist in the U.S. was of some $300 million of Rembrandts and other works stolen from Boston's Isabella Stewart Gardner Museum, in 1990.

Monet's "Poppies Near Vetheuil," Degas's "Count Lepic and his Daughters," Van Gogh's "Blossoming Chestnut Branches" and Cezanne's "Boy in the Red Vest" are the four paintings stolen, Swiss police said. A reward of 100,000 Swiss francs ($90,690) is being offered for information leading to the recovery of the paintings.

One of the men threatened personnel with a pistol, forcing them to the floor, while the other two robbers grabbed the paintings from the exhibition hall. One of the robbers spoke German with a Slavic accent, the police said.

Gang prepared

"It sounds like there was a gang prepared to do anything to get the art," said Chris Marinello, the London-based general counsel of the Art Loss Register, which listed the stolen paintings on its data base after being approached by the museum.

"You could infer that from the number of people involved in the theft and the fact that it was well-planned, a half hour before the museum was about to close," Marinello said.

The culprits didn't steal more because of the weight of the framed paintings, Gloor said. The museum had adequate security and was powerless against an armed robbery, he said.

"The choice of the room was very targeted while the choice of the pictures was in the line they were hanging" and nearest to the door, Gloor said, adding that he couldn't say whether the culprits targeted specifically the most valuable picture, the Cezanne.

Reward money

Criminals may use art to obtain the reward money, or sell it to raise cash for illicit activities such as weapons traffic, Marinello said. While the paintings can't easily be sold in the open market, "there is always someone who is willing to buy them at a discount and hold them." Later, the art may be used by the buyer to raise cash from somebody else in the black market, he said.

If the thieves do try to sell the paintings, they will probably do so in another country, perhaps through a smaller dealer or auction house. Their job will be harder because the art is listed as stolen by the Art Loss Register, Marinello said.

The bill could have been heavier for the museum, which houses some 200 paintings, including seven Van Goghs, seven Cezannes, six Degas and five Monets.

Emil Buerhle, who studied history of art in Germany, took over machinery maker Schweizerische Werkzeugmaschinenfabrik Oerlikon, near Zurich, in the late 1920s. He became a Swiss citizen in 1936. The company changed its name to Oerlikon-Buehrle and expanded into weapons. It later drew fire for its role during World War II.

Arms Exports

From 1940 to 1944, the company accounted for 52 percent of arms exports from Switzerland, according to customs statistics analyzed by historian Peter Hug as part of a study into Switzerland's role during the war.

Buehrle purchased most of the paintings between 1951 and until his death in 1956. The Foundation museum is housed in a villa adjoining his former home, according to the museum's Web site.

Two Pablo Picasso oil paintings belonging to the Sprengel Museum in Germany were stolen on Feb. 6 from a cultural exhibit in eastern Switzerland, police said. The thieves involved are still at large. Police officials told Agence France-Presse the Picasso works had a total value of almost $4.5 million.

Museums including in the U.S. often don't have the money to spend on adequate security, according to Marinello.

Rising art prices

Rising art prices have swollen the value of art thefts. Prices for modern art, including Pablo Picasso, have risen 2.5 times since 2002, according to Art Market Research's index of the central 50 percent of works.

While investor losses in the financial markets have made it harder to sell some impressionist and modern works at peak prices, the most desired pictures continue to appreciate. A Picasso painting of his mistress Dora Maar sold for 5.7 million pounds ($11.1 million) with commission on Feb. 4, after failing to sell in 2002 at a low estimate of $4 million.