"A robbery took place this morning at the opening of the Louvre Museum," Culture Minister Rachida Dati wrote on X.
The museum cited "exceptional reasons" for the closure. No injuries were reported.
The Interior Ministry said several intruders forced open a window about 9.30am on Sunday, stole jewels from vitrines and fled on two-wheelers.
The ministry said forensic work was under way and a precise inventory of the stolen objects was being compiled, adding that the items have "inestimable" historical and patrimonial value.
Dati and Interior Minister Laurent Nunez were on site with museum leadership.
Police sealed off the museum and evacuated visitors. New arrivals were turned away and nearby streets were closed, according to the Interior Ministry.
Nunez called it a "major robbery", saying the intruders "entered from the outside using a basket lift", that the operation lasted seven minutes, and that the panes were cut with a disc cutter.
He said it was "manifestly a team that had done scouting".
Separately, the Interior Ministry specified the location as the Galerie d'Apollon.
Le Parisien reported the thieves entered via the Seine-facing facade, where construction is under way, and used a freight elevator to reach the gallery.
After breaking windows, they reportedly stole nine pieces from the jewellery collection of Napoleon and the Empress, the paper said.
Le Parisien also reported that one stolen jewel was later found outside the museum.
Citing early investigative findings, the paper said it was believed to be Empress Eugenie's crown and that it had been broken.
The Louvre has a long history of thefts and attempted robberies.
The most famous was in 1911, when the Mona Lisa vanished from its frame, stolen by Vincenzo Peruggia, a former worker who hid inside the museum and walked out with the painting under his coat.
It was recovered two years later in Florence - an episode that helped make Leonardo da Vinci's portrait the world's best-known artwork.
In 1983, two Renaissance-era pieces of armour were stolen from the Louvre and recovered almost four decades later.
The museum's collection also bears the legacy of Napoleonic-era looting that continues to spark restitution debates today.
The Louvre is home to more than 33,000 works spanning antiquities, sculpture and painting - from Mesopotamia, Egypt and the classical world to European masters.
Its star attractions include the Mona Lisa, the Venus de Milo and the Winged Victory of Samothrace.
The Galerie d'Apollon, where Sunday's theft reportedly took place, displays a selection of the French Crown Jewels.
The museum can draw up to 30,000 visitors a day.
