Two men bought tickets to enter Vienna's Museum of Applied Arts (MAK) before smashing a display case, grabbing a 200-carat platinum and diamond necklace and walking away, police said on Friday.
Austrian media said the Van Cleef and Arpels necklace, with 673 precious stones, was worth several million dollars. It is the latest in a series of high-profile heists to hit European museums.
Police said the two men did not wear masks, paid to enter the museum and were clearly seen on surveillance cameras in Thursday's heist.
They "smashed a glass display case" with a hammer before "fleeing with the jewellery in an unknown direction," said a police statement.
The MAK museum confirmed the theft but said it would not comment while the investigation went ahead.
The necklace had been part of an exhibition devoted to the French designers Van Cleef and Arpels. Some 500 pieces had been on display since June. The exhibition is scheduled to end on September 27.
Despite the MAK announcing the exhibition would remain closed until further notice, the wing where the theft occurred reopened hours later.
Reminiscent of Louvre heist
The stolen necklace was designed for the former Egyptian royal family and was worn by Queen Nazli in 1939 for the marriage of her daughter Faiza to the future Shah of Iran, Mohammad Reza Pahlavi.
On its website, Van Cleef and Arpels called the stolen piece a "triumph of white jewellery." The French company did not immediately comment on the theft.
European museums have been hit by a series of spectacular thefts since thieves in October broke into the Louvre museum in Paris in broad daylight, escaping in less than eight minutes with jewellery worth €88 million.
Thieves on Thursday raided the Treasure of Villena, one of the greatest Bronze Age gold collections, at a museum in the Spanish city of Villena, taking most of the 50-plus mainly gold bracelets, bowls, bottles and other items on display.
Four works "of extraordinary value" by Renaissance artist Antonello da Messina were stolen from a museum in Sicily, Italy's culture ministry said Sunday.
Two days earlier, Italian police said they had recovered paintings by Renoir, Cezanne and Matisse worth over €8 million which were stolen from the Magnani-Rocca Foundation museum near Parma.
