Art thieves have struck again in Switzerland, making off with a quartet of paintings by Paul Cézanne, Edgar Degas, Vincent van Gogh and Claude Monet, just days after a theft of Pablo Picasso works.

The armed gang targeted the collection of Emil Buehrle in Zurich.
(Keystone/Walter Bieri/Associated Press)

A trio of armed and masked men stormed into a gated Zurich villa a half-hour before the facility was set to close on Sunday and forced staffers to the ground during the daylight theft, police said on Monday.

The three men behind what police called "a spectacular art robbery" escaped in a white car and remain at large.

Located in a tony district on an outer edge of Zurich, the villa houses an important private collection of impressionist and post-impressionist artwork amassed by the late industrialist Emil Buehrle.

The four stolen 19th century oil paintings, estimated to be worth a total of 180 million Swiss francs (nearly $163 million), are:

• Cézanne's The Boy in Red Waistcoat.
• Degas's Viscount Ludovic Lepic and His Daughter.
• Monet's Poppy Field Near Vetheuil.
• Van Gogh's Blooming Chestnut Branches.

A police spokesperson called the brazen robbery the largest in Switzerland's history and one of the biggest ever in Europe. A reward of about $90,000 was offered for information that leads to the recovery of the four works.

At a news conference Monday, Lukas Gloor, the museum's director, described the four stolen works as among the collection's most important paintings.

However, he said that the robbers appeared to have taken the first four they saw, leaving even more valuable paintings hanging in the same room.

"We are happy that no employees or visitors were hurt," Gloor added.

Switzerland's second heist in a week

Sunday's heist comes just days after another major art theft in Switzerland. Last week, the Pablo Picasso paintings Tête de cheval and Verre et pichet were stolen from an exhibit featuring the cubist master's works on display in a cultural centre not far from Zurich.

The two paintings had been on loan from Germany's Sprengel Museum in Hanover.

Police said Monday they are still investigating the Picasso theft and declined to say whether they consider the two art heists to be connected.

"Stealing artwork from museums has become somewhat of a glamorous exercise," Andrew Gibbs of Canada's Heffel Fine Art Auction House told CBC News Monday afternoon.

"The difficult thing in terms of valuing these pieces is that once they're stolen, they're essentially valueless," said Gibbs, director of appraisal services for Heffel's eastern division.

He pointed out that because of their high profile and the fact that agencies like Interpol, the FBI and the Art Loss Register keep detailed information about thousands of artworks stolen each year, the paintings can be tracked if they ever resurface into the market.  

With files from the Associated Press