The cause of the fire was not immediately known.
The building, which is situated next to the Christiansborg Palace where the parliament sits, is a popular tourist attraction. Its distinctive spire, in the shape of the tails of four dragons twined together, reached a height of 56 metres (184 feet).
Huge billows of smoke rose over downtown Copenhagen, and people were seen rushing inside the building to save paintings.
Danish Culture Minister Jakob Engel-Schmidt said it was “touching” to see how passers-by helped emergency services “to save art treasures and iconic images from the burning building.”
Horrible pictures from the Bourse. So sad. An iconic building that means a lot to all of us … Our own Notre-Dame moment
“Horrible pictures from the Bourse. So sad. An iconic building that means a lot to all of us … Our own Notre-Dame moment,” Defence Minister Troels Lund Poulsen wrote on X.
Ambulances were at the scene, but there were no reports of casualties. Members of an army unit were seen being deployed to cordon off the area, and the Danish Emergency Management Agency was also helping out.
The building was completed in 1625, and is one of the oldest in Copenhagen. The building is currently undergoing renovations and is covered in scaffolding.
The renovation was intended to correct previous work carried out in the 19th century, and restore the building’s facade to its original appearance.
The roof, masonry, sandstone and spire of Boersen, built in 1615 and considered a leading example of Dutch Renaissance style in Denmark, said the Danish Chamber of Commerce, which moved into the building after Copenhagen’s stock exchange left in 1974.
The chamber’s head, Brian Mikkelsen, was among those helping to carry paintings out of the building. “It is a national disaster,” Mikkelsen told reporters.
The adjacent Christiansborg Palace has burned down on several occasions, and most recently in 1990 a fire broke out in an annex of the Danish parliament, known as Proviantgaarden. However, the Old Stock Exchange survived unscathed.
That annex, which lies in the block behind the Old Stock Exchange, was evacuated as a precaution, as were different ministries in the street behind the burning building.
Beside housing the Chamber of Commerce, the Old Stock Exchange is used for gala dinners, conferences, parties and other events.
Police said on the social media site X that a main road in Copenhagen was closed and people should expect the area to be cordoned off for some time. Several bus queues were diverted, and Danish media reported huge traffic jams in the surrounding area.
Reporting from Bloomberg, Reuters, Associated Press, dpa