Parisians and tourists were in a state of sadness as the French capital's Notre Dame cathedral was still smouldering on Tuesday, as firefighters extinguished the remains of the devastating fire that swept through the building on Monday evening.

"I am really sad, I am deeply aghast. I am a Parisian, so I have always lived here, I was born here. And even if one is a believer or not it is our heritage, these are Christian roots that belong to France, that belong to Europe," said Paris resident Jean Claude.

"It is like a symbol of France has disappeared in a few hours," said Paris resident Claire.

"As if by chance, [this happened] during the Holy Week. So it's not an accident," speculated one woman.

Referring to the suggestion US President Donald Trump made on Twitter on Monday to put out the fire with "flying water tankers," Jean Clause said that "hurling tonnes of water on a religious building built some centuries ago is perhaps not the most appropriate solution."

The iconic spire of the centuries-old Gothic structure, as well as large parts of the roof, collapsed during the conflagration, which is now reportedly under control.

The cause of the blaze is not yet known, although there are indications that it may be linked to restoration work that was underway at the cathedral.

The main structure of the building, including its two bell towers, has reportedly been saved and is no longer in danger of collapse.

French President Emmanuel Macron has pledged to rebuild the 12th century cathedral and an international fundraising campaign is under way to gather money for the repairs.