Thieves have managed to steal two crowns and an orb from the Swedish royal family.
Police said the priceless items were taken at lunchtime on Tuesday from a cathedral in Strängnäs, around an hour west of the capital Stockholm.
Witnesses said the culprits escaped in a speedboat that was waiting nearby on Lake Malaren, the country's third largest lake.
The robbers snatched the valuables after smashing a glass case that held the funeral regalia of King Karl IX and his wife Queen Kristina. The crowns and orb are adorned with precious stones and gold as well as pearls.
Police made public the details of the robbery in an attempt to identify the thieves.
"We want to spread information and pictures of these items so that they can be identified as stolen objects," police spokesman Thomas Agnevik said.
King Karl IX died in 1611 and his wife Queen Kristina in 1625. The items are priceless and police said that the objects would be very hard to sell on the open market.
"What usually happens with this type of object is that they are recovered sooner or later because there are very few people who are prepared to handle such items," Agnevik said.
"We have high hopes of getting them back."