Jewellery worth more than $1m which was due to be loaned to film stars has been stolen from a Cannes hotel in a pre-dawn heist.

An American female employee of Swiss jewellers Chopard told police on Friday that thieves had plundered her hotel room and ripped out the strongbox in the wardrobe.

Police said the safe and the jewels inside it had been stolen in the raid, which has been compared to the scenario of a movie worthy of screening at the Cannes Film Festival, where actors were due to wear the stolen jewels.

Commander Bernard Mascarelli, a judicial police spokesman in the nearby city of Nice, said the robbery took place about 2am (00:00 GMT) on Friday at the Novotel hotel near the festival venue.

Mascarelli said police were trying to verify the exact value and type of the jewels stolen, but sources said it was a "matched set".

However, Jean-Michel Caillau, the prosecutor in nearby Grasse who is leading an investigation, said that early estimates were that the jewels could have been worth as much as $1.4m.

Authorities were going over hotel surveillance cameras and questioning potential witnesses who might have seen any culprits, who struck hours after the festival's world premiere of The Bling Ring, a true tale of wealthy teenagers who burgle the homes of Hollywood celebrities.

'Inside complicity'

"It seems pretty unlikely to us that it was just one person," Mascarelli said.

"Apparently this [hotel guest] was someone who was targeted because it wasn't someone who had been seeking attention.

"There must have been either an inside complicity, or people who were in contact with this person and knew that the person had jewels."

Officers said they were examining footage from the southern French city's security cameras in the hope of finding clues.

Chopard is one of the official sponsors of the festival, and one of its stores, complete with its own red carpet, lies on the palm-fringed beachfront, just opposite the venue.

The jeweller redesigned the coveted Palme d'Or trophy and each year lends out jewellery to stars for their walk up the red-carpeted steps at the Palais des Festivals.

The Palme d'Or features 118g of yellow gold, with a value of more than 20,000 euros ($26,000), and is set in a base of rock crystal.

The Cannes Film Festival is ranked as the world's most prestigious movie showcase and is held amid tight security, as it lures thousands of wealthy actors, directors, producers and movie buyers.

Festival organisers would not disclose the Palme's whereabouts on Friday, but said it was kept in a safe place.

The festival had no comment on the robbery.

Spokeswomen for Chopard and Novotel owner Accor also declined comment.