The Louvre museum was hit by a brazen daytime jewel heist, forcing the Paris institution to close its doors for a second day in a row.

Museums across France have been ordered to increase security after eight royal pieces of jewellery were stolen from the Louvre museum in Paris.

Authorities were racing Monday to reassure the public about security at key cultural sites — and find the jewels stolen from the museum before they can be broken up and melted down.

A minute-by-minute look at the daring Louvre robbery, using maps, photos and video to unravel how one of the world’s most famous museums was breached.

France will review the protection of cultural sites across the country and beef up security if needed, officials said on Monday as a manhunt was under way for the four people who staged an audacious daylight robbery at the Louvre museum.

High visitor numbers and dwindling funds for overhauls may have made the landmark museum unexpectedly vulnerable.

Thieves broke into the Louvre in Paris — the world's most visited museum — early Sunday morning. Museum officials said they stole jewelry and fled.

A manhunt is underway to find the four thieves before the jewels - which once belonged to French royals - are broken up.