Armed robbers snatched jewels worth millions from a work by famed Parisian goldsmith Joseph Chaumet and classed a national treasure in a brazen heist at a French museum.

Motorbike-riding thieves arrived at the Hieron Museum in Paray-le-Monial in central France at around 4:00 pm (1500 GMT) on Thursday.

Three entered the building and one stood guard outside, mayor Jean-Marc Nesme said.

The group fired several shots before heading for the museum's star exhibit, a three-metre work executed in 1904 depicting the life of Christ in precious metals, jewels and ivory.

Known as "Via Vitae", it is classed as a national treasure by France's culture ministry, with an estimated value of up to seven million euros (US$7.3 million), mayor Nesme said on Friday.

The intruders sawed through the armoured glass protecting the piece with a power tool before snatching gold and ivory figurines as well as emerald decorations from the piece.

The gigantic piece comprises 138 figures encrusted with diamonds and rubies set in marble of various shades and alabaster.

As they fled on their motorbikes, the gang sowed spikes across the road to hobble two pursuing vehicles, police said.

"This is a great loss for Paray-le-Monial and for national heritage", mayor Nesme said.

Staff and around 20 visitors present on the museum's ground floor had been "traumatised" by the violent intrusion, he added.

The Hieron Museum, one of France's oldest for sacred art, has previously been targeted by thieves.

Two gold crowns were stolen in 2017, while there was another attempted robbery in 2022.

Thursday's theft came a day after several precious objects including ornate snuffboxes were stolen from a central Paris museum.

The broad daylight robbery saw thieves break into a display case with axes and baseball bats in full view of visitors and staff at the Cognacq-Jay museum. (AFP)