President Emmanuel Macron vowed to rebuild the Notre-Dame Cathedral, the medieval architectural jewel at the heart of Paris, as the country's wealthy on Tuesday pledged hundreds of millions to fund reconstruction.
Messages of support and condolences flooded in from heads of state while more than €600 million was pledged for the reconstruction.
Less than 24 hours after the fire broke out, Mr Macron and Pope Francis promised to restore the Roman Catholic church that dates back to 1160.
“Notre-Dame is the architectural gem of a collective memory, a place of gathering for great events, a witness of the faith and prayer of Catholics in the heart of the city," the pope said.
As the flames destroyed the roof and spire, Mr Macron sought to unify his nation “We will rebuild this cathedral, all of us together," he said.
A special Cabinet meeting was held on Tuesday and Mr Macron sent thanks to world leaders including US President Donald Trump.
Dr Anwar Gargash, UAE Minister of State for Foreign Affairs, was in Paris on Monday to meet French politicians, and indicated that he had watched skyline as the church burned.
“Very saddened by the terrible fire destroying the great cathedral of Notre-Dame,” he wrote on Twitter. “A sacred landmark important to France and beyond. Terrible catastrophe to see this unfold.”
As the cathedral went up in flames, another fire raged in Al Aqsa Mosque in Jerusalem.
Palestinian President Mahmoud Abbas issued a message of solidarity with the French capital.
"The Presidency confirmed its solidarity and sympathy with our friends in France over this incident," Mr Abbas said.
Sheikh Ahmed Al Tayeb, Grand Imam of Egypt's Al Azhar, the Muslim seat of learning, added his sympathies.
"Our hearts are with our brothers in France," he said.
Visited by 13 million people a year and the setting for Victor Hugo's 1831 novel The Hunchback of Notre Dame, Our Lady of Paris survived revolutions and world wars. No one died in the fire.
A budget to restore the cathedral had been set before the fire at €150m and officials estimated at least €450m would be needed, said Michel Picaud, president of the Friends of Notre-Dame de Paris.
Billionaire François-Henri Pinault, chairman and chief executive of the Kering group that owns the Gucci and Yves Saint Laurent fashion brands, pledged €100m towards rebuilding Notre-Dame.
Bernard Arnault's family and their company LVMH, a business empire that includes Louis Vuitton and Sephora, promised €200m.
Tim Cook, chief executive of Apple, also pledged to underwrite reconstruction while Total, the French oil giant, pledged €100m.
The French charity Fondation du Patrimoine said it would launch an international appeal for funds for the cathedral.
Investigators said the cause of the fire was probably an accident linked to repair work that was being done.
Those involved in the repair effort expressed deep remorse at the blaze, which was brought under control after a 12-hour battle involving more than 1,000 firefighters.
Julien Le Bras, the scaffolding company boss, shared his distress at the tragedy.
“It is with unqualified sadness I am speaking,” Mr Le Bras said. “The police investigation is taking place and our workers will help answer questions with no reserve whatsoever to throw light on the cause of this drama.
"At the moment the fire started none of the workers of my company was present. All security and fire requirements were respected.
“I extend my sincere admiration to the emergency services who have risked their lives to try to save this important national monument.”
Tributes were paid to a line of volunteers organised by a Catholic priest to save the most important artifacts in the Cathedral, including the crown of thorns believed to have been worn by Jesus before his crucifixion.
There was also a tunic which King Louis IX is said to have worn when he brought the crown to Paris.
While experts lamented the loss of the intricate wooden structure of the roof and interior, it was pointed out that an avenue of oak trees had been planted at Versailles in the 19th century to provide replacement wood in case of a fire.
Donald Tusk, President of the European Council, called on all 28 members of the EU to support the reconstruction.
Drawing on the history of his native Poland where Warsaw was rebuilt after the Second World War using paintings by Venetian artists as guides, Mr Tusk said the ashes need not represent the last word.
“You will manage, this is not the end of the world,” he said.
Queen Elizabeth II added her sympathies in a letter.
“My thoughts and prayers are with those who worship at the cathedral and all of France at this difficult time," she said.
Former US first lady Michelle Obama was in Paris on the latest leg of her book tour and spoke of her memories of visiting Notre-Dame.
"Being here in Paris tonight, my heart aches with the people of France," she wrote. "Yet I know that the Notre-Dame I experienced all those years ago, as so many others have over the centuries, will soon awe us again."
But it will be a long time before the tragedy is repaired and Camille Pascal, a French historian, said Parisians would miss the everyday sights and sounds of the cathedral.
"Happy and unfortunate events for centuries have been marked by the bells of Notre-Dame,” Mr Pascal said. “We can be only horrified by what we see."
Around the world, comparisons were made to other great fires and their after-effects.
In Britain, many talked of rebuilding York Minster in the 1980s after a lightning strike, and Windsor Castle in the 1990s after a blaze.
In China, people online drew comparison with the burning of Yuanmingyuan, the summer palace of the Qing dynasty, in 1860 during a conflict between British and French forces with imperial Chinese.
Moon Jae-in, South Korean President, said the rebuilding process could bring the world together.
“Our love for humanity will be illustrated in a more mature way in the process of reconstruction,” Mr Moon said.
Meanwhile, within France the consequences of the disaster started to play out on the political stage.
The priceless art and artefacts housed inside the Notre-Dame - in pictures
The fire prompted the cancellation of a speech by Mr Macron to address the concerns of citizens angered over economic disparity and dysfunctional politics after months of protests by the Yellow Vests movement.
It was hoped the speech would raise his popularity, which had taken a battering from a public perception that he is out of touch and that his policies favour the rich.
“This is an opportunity for Macron to reach out to the opposition to create unity in a fractured, divided nation,” said Bruno Cautres, a politics professor at Sciences Po Institute.
“He can’t be seen as using this moment of widespread grief but at the same time, people will expect all politicians to start working together, first for Notre Dame and hopefully beyond.”