Firefighters managed to save the 850-year-old Gothic building's main stone structure, including its two towers, but the spire and roof collapsed.

The fire was declared under control almost nine hours after it started.

The cause is not yet clear but officials say it could be linked to extensive renovation works under way.

Paris prosecutor's office said it was currently being investigated as an accident. A firefighter was seriously injured while tackling the blaze.

Macron: 'Terrible tragedy'

Visiting the site on Monday night, Mr Macron said the "worst had been avoided" with the preservation of the cathedral's main structure as he pledged to launch an international fundraising scheme for the reconstruction.

• In pictures: Blaze at Notre-Dame
• What makes the cathedral so special

"We'll rebuild this cathedral all together and it's undoubtedly part of the French destiny and the project we'll have for the coming years," said Mr Macron.

"That's what the French expect [and] because it's what our history deserves," he added, visibly emotional, calling it a "terrible tragedy".

Billionaire François-Henri Pinault, chairman and CEO of the Kering group that owns the Gucci and Yves Saint Laurent fashion brands, has already pledged €100m (£86m; $113m) towards rebuilding Notre-Dame, AFP news agency reports.

The French charity Fondation du Patrimoine is launching an international appeal for funds for the cathedral, a Unesco World Heritage site.

The fire started at around 18:30 (16:30 GMT) on Monday and quickly reached the roof of the cathedral, destroying its stained-glass windows and the wooden interior before toppling the spire.

Firefighters then spent hours working to prevent one of the iconic bell towers from collapsing. Search teams are now assessing the extent of the damage.

Sections of the building were under scaffolding as part of the renovations and 16 copper statues had been removed last week. Work began after cracks appeared in the stone, sparking fears the structure could become unstable.