The city’s deputy mayor said the iconic building had suffered “colossal damages” amid fears its entire wooden frame, dating back 850 years, would not survive. France’s interior ministry said firefighters might not be able to save the structure.
President Emmanuel Macron arrived at the scene as it emerged the fire had spread to one of Notre-Dame’s famous rectangular towers, and said it was being treated as a national emergency.
Earlier he told his compatriots that a “part of us” is on fire as hundreds of stunned Parisians lined the banks of the Seine to watch the cathedral burn.
A spokesman said the entire wooden frame of the cathedral would probably come down, and that the vault of the edifice could be threatened too, with work under way to save priceless art works including paintings dating back to the 17th century.
Paris mayor Anne Hidalgo described it as a “terrible fire” and urged people at the scene to stay safe.
The cause of the blaze was not known, but French media quoted the Paris fire brigade as saying the fire is “potentially linked” to a €6 million (£5m) renovation project on the church’s spire. Prosecutors opened an investigation as Paris police said there were no reported deaths.
Flames shot out of the roof behind the nave of the cathedral, among the most visited landmarks in the world. The fire came less than a week before Easter amid Holy Week commemorations.
President Macron tweeted: “Our Lady of Paris in flames. Emotion of a whole nation. Thought for all Catholics and for all French. Like all our countrymen, I’m sad tonight to see this part of us burn.”
As a result of the fire, the French president has postponed an important address to the nation that was to lay out his responses to the yellow vest crisis.
Notre-Dame spokesman Andre Finot told French media: “Everything is burning, nothing will remain from the frame.”
A masterpiece of Gothic architecture, Notre-Dame has loomed large on the Paris skyline and in the French psyche since the Middle Ages, surviving the Revolution and the Second World War.
It was immortalised in Victor Hugo’s 1831 novel Notre-Dame de Paris, published in English as The Hunchback of Notre-Dame, and among the most celebrated artworks are its three stained-glass rose windows, high on the cathedral’s west, north and south faces. Its priceless treasures also include a relic, the crown of thorns, which is only occasionally displayed, including on Fridays during Lent.
French writer and historian Camille Pascal said the fire had caused “the destruction of invaluable heritage” and “we can be only horrified by what we see”.
Speaking to French broadcaster BFMTV, he said: “It’s been 800 years that the cathedral watches over Paris” and its bells pealed for both “happy and unfortunate events”. He recalled that Notre-Dame’s bells sounded a death knell after the November 2015 terror attacks in Paris.
Authorities are investigating if renovation work was a factor in starting or spreading the fire, although the cause remains unknown.
US president Donald Trump caused consternation after suggesting the fire could be extinguished with “flying water tankers”.
“So horrible to watch the massive fire at Notre- Dame Cathedral in Paris,” he tweeted. “Perhaps flying water tankers could be used to put it out. Must act quickly!”
France’s civil security agency said “all means” except for water-dropping aircraft were deployed to tackle the blaze.
The agency said those were unsuitable for fires like the one at Notre-Dame because dumping water on the building could cause the whole structure to collapse.
Last week, 16 religious statues were removed from the peak of the building for the first time in over a century to be taken for cleaning and therefore escaped the blaze.
Last night photos and videos on social media showed the roof of the cathedral covered in flames, issuing a plume of smoke above the city.
The Paris fire brigade can be seen in videos dousing the blaze with water.
Ashley Huntington, 21, an American student studying in Paris, said: “You could just get close and see the smoke. The smoke is everywhere. It seems like pieces of the scaffolding are currently falling.”
She added: “It just looks like it’s out of control. I’ve never seen a fire in real life but the flames keep getting bigger and bigger. I don’t think it’s getting better at all.”
Labour MP Yvette Cooper, who was in Paris, said: “Have just come away from the bank of the Seine after the spire fell as I can’t bear to watch any more. Fearful for anyone close to the flames, and aghast that centuries of history & beauty could disappear into smoke so fast.”
First Minister Nicola Sturgeon tweeted: “This is truly devastating. What a cultural tragedy, not just for Paris and France, but for the world.”
Former US presidential candidate Hillary Clinton said she wished France strength “as they grieve and rebuild”. “My heart goes out to Paris,” she tweeted. “Notre-Dame is a symbol of our ability as human beings to unite.”