A fire ripped through Copenhagen's Old Stock Exchange, one of the Danish capital's best-known buildings, on Tuesday, engulfing its spire which collapsed in a scene reminiscent of the 2019 blaze at Paris' Notre-Dame.

Parts of the roof had collapsed and the fire spread to several floors of the building, Copenhagen fire department chief Jakob Vedsted Andersen told reporters.

There were no immediate reports of injuries, police said.

People were seen carrying large paintings away from the building to save the historic artefacts from the flames.

"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.

Thick grey smoke rose above the city and sirens could be heard as emergency services were called to the site. Around 90 conscripts from the Royal Life Guards, an army unit, were helping cordon off and secure valuables, the military said.

The historic building, whose spire was shaped as the tails of four dragons intertwined, had been under renovation and clad in scaffolding when the fire broke out.

The Dutch Renaissance style building no longer houses the Danish stock exchange, but serves as headquarters for the Danish Chamber of Commerce.

"We are currently working hard to save our historical art from the Bourse," the Chamber of Commerce wrote on X.

Dragons on the roof

The presence of dragons on the roof had been seen as symbolically protecting the exchange from enemies, as well as from fire, the Chamber said on its website.

The scaffolding around the building made it harder for the emergency services to get through to the flames, while the copper roof was trapping the heat.

"We are saving everything we possibly can," a spokesperson for the fire department told reporters.

The nearby finance ministry was evacuated as a result of the fire, the police said.

It was not immediately clear what caused the blaze.

Copenhagen police asked people to avoid driving in the inner part of the city.

The Danish Chamber of Commerce, which has owned the building since 1857, has worked on restoring it to the style of Denmark's King Christian IV, who had the building constructed in the 17th century.

"400 years of Danish cultural heritage in flames," Culture Minister Jakob Engel-Schmidt wrote on X. "The building is filled with art that tells a lot about our history, about who we are as a people," he told reporters.