According to various media reports, two thieves in balaclavas breached the museum using a crane and smashed an upstairs window, while a third suspect reportedly served as a lookout. Using a freight elevator, two suspects entered the Apollo Gallery.
They stole eight pieces from the Crown Jewels, including a necklace, a brooch and a tiara.
Alarms sounded during the theft, bringing security to the scene and forcing the intruders to flee. Four suspects reportedly left the scene on motorbikes.
The museum has not assessed the total amount of the loss and some have suggested that the theft has all the hallmarks of the notorious Pink Panthers gang.
Among the lost items are pieces owned by Emperor Napoleon, his nephew Napoleon III and their wives, the empresses Marie-Louise and Eugénie.
Among the stolen items is the diamond brooch of Empress Eugénie, which was worn during a visit by Queen Victoria in 1855.
A necklace and earrings from the sapphire jewellery set of Queen Marie-Amélie and Queen Hortense are also missing, as are the emerald necklace and earrings from the Marie-Louise set, gifted by Napoleon to Marie-Louise as part of their marriage in 1810.
A brooch known as the Reliquary Brooch and a tiara of Empress Eugénie were also stolen, and the thieves reportedly dropped a crown made of gold, emeralds, and more than 1,300 diamonds. The crown of Empress Eugénie was reportedly discovered broken outside the museum.
Among the items left behind is the Regent Diamond, a 140-carat diamond that was mined in India and cut in London before being purchased by the regent of France in the early 18th century.
Backgroud reading: Pink Panthers: Europe's mysterious gang of jewellery thieves
The diamond has an estimated value of more than $AUD100 million, and Paris prosecutor Laure Beccuau told ABC News that it is unclear why such an obvious and high-profile target was not stolen.
"It will only be when they're in custody and face investigators that we'll know what type of order they had and why they didn't target that window,” Beccuau explained.
"We're looking at the hypothesis of organised crime. Nowadays, anything can be linked to drug trafficking, given the significant sums of money obtained from drug trafficking."
This stunning incident has raised new questions about the quality of security at the Louvre Museum, which houses famous artworks such as the Mona Lisa, and welcomes more than 8 million visitors each year.
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