A lone thief broke into a major Paris gallery and made off with a 120-million-dollar haul of modern masterpieces, including works by Matisse and Picasso, officials said Thursday.

In this 2006 photo, a woman looks at the painting "Olive Tree near Estaque" by French painter Georges Braque. A lone thief has stolen 500 million euros worth of paintings, including masterpieces by Henri Matisse and Pablo Picasso, in one of the world's biggest art raids, officials have said. (AFP/File/Anne-Christine Poujoulat)

The thief sheared off a gate padlock and broke a window to get into the Musee d'Art Moderne and then disabled the alarm system to carry out the brazen night-time heist. The paintings were found to be missing just before the museum was to open Thursday.

The major tourist attraction, near the Eiffel Tower, was sealed off as police sought clues to who was behind the latest stunning robbery that raised new questions about museum security in the French capital.

"According to estimates by the management of the Musee d'Art Moderne, the value of the stolen canvases totals between 90 and 100 million euros," said a spokesman for Paris city hall, which operates the museum.

Police and judicial sources had earlier said the haul was worth 500 million euros (617 million dollars), but art experts said this was unlikely.

"The Picasso might be worth 40 to 50 million euros, the Braque 10 to 20," said Didier Rykner, editor of the specialist magazine The Art Tribune.

"But in any case, we're talking about a theoretical value, they don't have a market value, because you couldn't openly sell them. They're too well known."

Video surveillance cameras recorded only one person entering through a window. Police gave few other details of what happened, although the city spokesman said an alarm system had been over-ridden.

Besides the Henri Matisse and the Pablo Picasso, works by Georges Braque, Ferdinand Leger and Amedeo Modigliani were also plucked from the walls of the city-run museum, one of the most-visited in the French capital.

The stolen paintings included Picasso's cubist "Dove with Green Peas," which the Spanish artist created in 1912, and his French contemporary Matisse's "Pastoral" from 1905.

The others were Braque's "Olive Tree near Estaque", Modigliani's "Woman with a Fan" and Leger's "Still Life with Candlestick".

Paris mayor Bertrand Delanoe expressed shock at the theft which he called "an intolerable attack on the universal cultural heritage in Paris."

The burglary is the biggest since four paintings by Cezanne, Degas, Van Gogh and Monet valued at more than 180 million Swiss francs (127 million euros, 162 million dollars) were stolen from a Zurich museum in February 2008.

France has seen a growing number of art thefts in recent months.

In January, about 30 paintings -- including some by Picasso and Henri 'Douanier' Rousseau -- were stolen from a private villa in the Cote d'Azur, with a total estimated value of around one million euros.

On New Year's Eve, a pastel by Edgar Degas disappeared from the Cantini museum in Marseille, also in the south of France. The 1877 painting worth 800,000 euros had been lent for an exhibition by the Musee d'Orsay in Paris.

It had been unscrewed from the wall and there was no evidence of a break-in, police said, indicating the thief or thieves knew how to get round the museum's security system.

In June last year, the Picasso Museum in Paris was robbed in broad daylight of a book of drawings by the celebrated 20th century artist, worth an estimated three million euros.

Stolen masterpieces are rarely recovered, but three men are being tried in France for the 2007 theft of three Picassos worth more than 50 million euros from the Paris home of his grand-daughter Diana Widmaier-Picasso.

The paintings were found after a five-month investigation.

Located in the well-heeled 16th arrondissement or district in leafy western Paris, the Musee d'Art Moderne is operated by the city authorities and is home to more than 8,000 20th century works of art.