A man on an electric scooter had burst into the shop carrying a handgun, police said.
Two suspects have been arrested in France on suspicion of robbing a high-profile jeweller in Paris.
Precious stones and jewellery were stolen from the Chaumet boutique near the Champs-Elysées on Tuesday afternoon.
A man on an electric scooter burst into the shop at around 17:00 CEST carrying a handgun, police said.
CCTV footage showed a man in a grey suit pretending to be a customer before drawing the weapon and threatening staff. Authorities estimated the haul had a value between €2 million and €3 million.
But police said they had detained two men in eastern France on Wednesday morning, alongside a "substantial part" of the loot.
The suspects -- who were originally from Montenegro -- were arrested after travelling on a bus to Moselle near the French border with Germany, prosecutors added.
The two men are being held in police custody on charges of organised armed robbery.
Chaumet is one of France's oldest jewellery brands and its Paris boutique was previously targeted by robbers in 2009 when precious stones worth €1.9 million were stolen.