Macron said the dramatic fire had brought out the best in a country that has been riven with divisions.

“What we saw last night in Paris was our capacity to mobilise and to unite,” Macron, 41, said in a solemn address from his office in the presidential palace.

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France had over the course of its history seen many towns, ports and churches go up in flames, he said.

“Each time we rebuilt them,” he said, adding that the cathedral inferno had shown that “our history never stops and that we will always have trials to overcome”.

“This is not a time for politics,” added Macron, who had cancelled a speech planned on Monday evening on the response to the “yellow vest” protests.

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He visited the site of the fire late on Monday and promised then to rebuild the cathedral, parts of which date to the 12th century.

The cathedral spire was destroyed and its roof gutted but the bell towers were still standing and many valuable art works were saved after more than 400 firefighters worked to contain the blaze, finally quelling it 14 hours after it began.

Paris public prosecutor Remy Heitz said there was no obvious indication the fire was arson. Fifty people were working on what would be a long and complex investigation, officials said.

The fire swiftly ripped through the cathedral’s oak roof supports, where workers had been carrying out extensive renovations to the spire’s timber-framed supports. Police had begun questioning the workers involved, the prosecutor’s office said.

One firefighter was injured but no one else was hurt, with the fire starting at around 6.30pm after the building was closed to the public for the evening.

Firefighters examined the facade, with its spectacular 10-metre filigreed stained-glass rose window still intact. They could be seen walking atop the belfries as police kept the area in lockdown.

Investigators will not be able to enter the cathedral’s blackened nave until experts are satisfied its walls withstood the heat and the building is structurally sound.

“Yesterday we thought the whole cathedral would collapse. Yet this morning she is still standing, valiant, despite everything,” said Sister Marie Aimee, a nun who had hurried to a nearby church to pray as the flames spread.

Messages of condolence flooded in from around the world.

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Pope Francis, the leader of the Catholic Church, was praying for those affected, the Vatican said, adding: “Notre Dame will always remain – and we have seen this in these hours – a place where believers and non-believers can come together in the most dramatic moments of French history.”

Britain’s Queen Elizabeth expressed deep sadness while her son and heir Prince Charles said he was “utterly heartbroken”. Chancellor Angela Merkel offered German help to rebuild a part of “our common European heritage”.

Considered among the finest examples of European Gothic architecture, Notre Dame is visited by more than 13 million people a year. It sits on an island in the Seine, overlooking the Left Bank haunts of Ernest Hemingway and Pablo Picasso.

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“Notre-Dame de Paris is the cathedral of the people, of the people of Paris, of the French people, of the people of the world. It is part of those references of our history, of what we have in common, of what we share,” said French Interior Minister Christophe Castaner.

Paolo Violini, a restoration specialist for Vatican museums, said the pace of the fire’s spread had been stunning.

“We are used to thinking about them as eternal simply because they have been there for centuries, or a thousand years, but the reality is they are very fragile,” Violini said.

The company carrying out the renovation work said it would cooperate fully with the investigation.

“All I can tell you is that at the moment the fire began none of my employees were on the site. We respected all procedures,” Julien Le Bras, a representative of family firm Le Bras Freres.

Many relics and artworks were saved. At one point, firefighters, police officers and municipal workers formed a human chain to remove the treasures, including a centuries-old crown of thorns made from reeds and gold, and the tunic believed to have been worn by Saint Louis, a 13th century king of France.

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The French government was mobilising efforts to rebuild the iconic cathedral on Tuesday. French Prime Minister Edouard Philippe held a ministerial round for consultations on reconstruction, with Culture Minister Franck Riester and the minister for public accounts, Gerald Darmanin, in attendance. Paris Mayor Anne Hidalgo said she would hold a donor conference.

Meanwhile, major French companies pledged hundreds of millions of euros towards the reconstruction effort.

The donations include a €100 million (US$113 million) pledge from Kering luxury goods company owner Francois Henri Pinault and an announcement by the Ile-de-France region, which contains the French capital, that it would put forward €10 million.

It is unclear what the total cost of reconstruction will be.

Reuters, AFP and AP