“This is a serious crime to the heritage of humanity,” Christophe Girard, culture deputy for the mayor of Paris told a news conference.
“These are key paintings by major artists,” he said, adding the theft was committed by “one or more individuals who were obviously organised”.
Police have launched an investigation into the theft, a spokesman for the Paris prosecutor’s office said.
High profile thefts
The Musee d’Art Moderne, located in the well-off 16th arrondissement, a stone’s throw from the Eiffel Tower, is home to more than 8,000 works of art from the 20th century.
|Art theft timeline|
The museum, which had initially estimated the worth of the paintings at $600m, revised the figure later in the day.
The robbery has come amid a growing number of thefts in recent months.
In January, about 30 paintings, including some by Picasso and Henri Rousseau, were stolen from a private villa in the Cote d’Azur, with a total estimated value of around $1.2m.
On 31 January, a pastel by Edgar Degas disappeared from the Cantini museum in Marseille, also in the south of France.
The 1877 painting worth nearly $1m 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.
Stolen masterpieces are rarely recovered, but three men are being tried in France for the 2007 theft of three Picassos worth more than $62m from the Paris home of his grand-daughter.
The paintings were found after a five-month investigation.