PARIS (Reuters) -A jewellery heist at Paris' Louvre museum has cast France in a "deplorable" light, Justice Minister Gerard Darmanin said on Monday as opposition politicians criticised the government for what they branded a national humiliation.

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.

Telegram's Pavel Durov slams the French government after the Louvre jewel heist. Experts fear the gems are lost forever.

Museum heists, particularly ones involving historic and valuable items, have shocked the world and inspired mystery and suspicion for more than a century.

The masked gang, who remain at large, made off with nine items, including a crown, a tiara, necklaces and earrings.

More than 25 years before Sunday's heist at the iconic museum, a thief took a 19th-century painting in broad daylight.

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.

Thieves at the Louvre museum stole eight items of "incalcuable" value from a collection of French crown jewels, including items belonging to Empress Eugénie, Queen Hortense and more