Art thieves stole paintings by Pablo Picasso, Henri Matisse, Amedeo Modigliani and two other well-known artists from a Paris museum in a heist worth €100 million.
Officials from the Musee d'Art Moderne de la ville de Paris said they discovered the five paintings, which included works by Fernand Leger and Georges Braque, were missing after noticing a smashed window pane as they opened for business today.
"This is a serious crime to the heritage of humanity," Christophe Girard, culture deputy for the mayor of Paris told a news conference. Mr Girard said the theft was committed by "one or more individuals who were obviously organised."
Museum officials said the paintings were worth about €100 million in total, revising an earlier figure of €500 million released by the police and public prosecutors.
The theft is the latest to hit Paris after robbers stole 32 drawings at the Picasso Museum worth €8 million last June.
The works stolen today were Pablo Picasso's Dove with Green Peas, Henri Matisse's Pastorale, Georges Braque's Olive tree near l'Estaque, Amedeo Modigliani's Woman on the range and Fernand Leger's Still life with candlesticks.
Picasso's Dove - a painting dating from the Spanish master's Cubist period - is worth €22 million.
"These are key paintings by major artists," Mr Girard said.
A special unit of the interior ministry, the BRB, is in charge of the investigation.
Museum employees found a window had been broken at the rear of the east wing of the "Palais de Tokyo", which was built during the Universal Exhibition of 1937. The museum has sophisticated alarm systems, close circuit television and three guards were on hand last night.
"We must let the police find out how the security system was evaded especially as these three watchmen saw nothing and did not react," Mr Girard said.
Similar thefts have led investigators back to collectors who order the works for their own private collections.
The Musee d'Art Moderne is situated in the capital's upmarket 16th arrondissement, across the Seine river from the Eiffel Tower.