The two thieves launched their operation at around lunchtime on Tuesday, and two men were seen jumping into a motorboat that sat moored in the lake adjacent to the church before making their escape. Police searched for them by both water and air with no result.

“It's the Mälaren lake so they could have gone to Köping or Aboga to the west, or to Västerås, Eskilstuna or Stockholm to the east. We’re tracking all directions,” Thomas Agnevik from the Stockholm Police told news agency TT.

READ ALSO: Swedish royal regalia found in rubbish bags

The crowns were part of the funeral regalia of Charles IX, son of Gustav Vasa, who was buried in the cathedral in 1611. Along with his crown, the smaller crown worn by his wife who subsequently died in 1625 was also taken, as well as an orb and cross.

The king's crown is made of gold and decorated with jewels, silver and pearls, with the queen's is also made of gold. Both are highly valuable.

The precious items were stolen from a locked and alarmed display cabinet in the church. Police have asked any witnesses to contact them as they attempt to trace the thieves.

In 2013, a crown and sceptre used in the funeral of Sweden’s King Johan III were stolen from Västerås. They subsequently turned up in two large rubbish bags at the side of a highway following a tip-off to police.