About 15 armed raiders have hijacked two vans carrying millions of euros of jewels in France, ejected the drivers and driven away, police said.
Authorities are combing the Yonne region in Burgundy, south east of Paris, and surrounding areas for the attackers.
No one was injured in the attack and the drivers of the two vans were left at the scene unharmed.
Police said the vans were found burned in a forest near the site of the attack on the A6 highway connecting Paris and Lyon. The jewels were not recovered.
The perpetrators escaped in four cars and the two vans.
In November, two gunmen robbed a Cartier jewellery boutique in a tourist-filled Paris neighbourhood, fled police in a chase across the Seine River, took a hostage and then surrendered.
In 2013, the Cannes Film Festival was hit by two high-profile thefts. First, a gunman walked into a jewel show at the Carlton International Hotel, stole 136 million US dollars in loot, and disappeared down a side street. Then, two armed men made off with a haul of luxury watches on the same promenade.
Last month, eight people were convicted in connection with one of the most spectacular jewel thefts in recent French history at a Harry Winston boutique in Paris. In the 2008 hold-up, three cross-dressing gunmen stole about 92 million US dollars in goods.