A large fire broke out on Wednesday at an office building belonging to Danish pharmaceutical group Novo Nordisk, maker of weight loss drugs Ozempic and Wegovy, Copenhagen's fire service said.

"It's a massive fire. We have about 100 firefighters on site", fire service chief of operations Martin Smith told AFP, adding that everyone had been evacuated from the building.

"There's no one inside," he said.

Smith said the blaze broke out in a container at a Novo Nordisk construction site, and spread to the roof of an adjacent office building also belonging to the company.

Large plumes of grey smoke could be seen 30 kilometres (18 miles) from the fire in Bagsvaerd, in the northern part of greater Copenhagen, Danish news agency Ritzau reported.

The fire came less than a week after a blaze erupted on May 16 at another Novo Nordisk site under construction in Kalundborg, which had no impact on its drugs production.