French President Emmanuel Macron has vowed to rebuild Notre Dame after firefighters declared the 850-year-old world treasure's structure "saved" from ruin.
Notre Dame's spire has already collapsed, and firefighters claim its iconic rose glass windows have been destroyed in the devastating inferno.
But the French leader, speaking outside the still-smoking cathedral more than 500 firefighters had battled for hours to save, said Notre Dame would rise from the ashes.
The world leader said: “We will appeal to the greatest talents and we will rebuild Notre-Dame because that’s what the French are waiting for, because that’s what our history deserves, because it’s our deepest destiny”
He declared an international appeal would be launched to raise the funds to rebuild the Cathedral, shortly after firefighters declared the structure would survive and the two towers had been saved.
Prosecutors in France believe the fire started accidentally based on their preliminary investigation.
As crews begin to get the blaze under control, reports say a firefighter tackling the blaze was "seriously injured" amid the response to the massive fire.
Onlookers were seen singing hymns and applauding exhausted firefighters in moving scenes from Paris beaming out around the world.
Firefighters earlier claimed the 13th century stained glass windows that make the cathedral so instantly recognisable are gone.
"They exploded because of the heat of the blaze," one firefighter said.
They said the Rosette West, which was created in 1225, the Rosette North, created in 1250, and the Rosette South, which dates back to 1250 have been lost to the flames.
The final hours before they declared the structure protected were "crucial" to saving treasured landmark, a Paris Fire Department spokesman had said earlier as crews battled to contain the blaze.
Now, it appears looks like they have done just that. The Cathedral has been saved but the devastating images beaming around the world from Paris made the "colossal damage" its suffered plain to see.
The important Catholic site of worship went up in flames during Christianity's Holy Week of Easter.
"Everything is collapsing," a police officer near the scene was heard to say as Parisians and tourists watched in tears as a "symbol of Paris" burned before their eyes.
Paris Fire Chief Jean-Claude Gallet said it is unclear if city firefighters will be able to keep the blaze from spreading and causing more destruction.
Speaking outside the cathedral, he said "we are not sure we are capable of stopping the spreading" to Notre Dame's second tower and belfry.
He said: "If it collapses, you can imagine how important the damage will be."
Crowds have gathered from the River Seine's bridges and banks as emergency services try desperately to save the medieval building and the priceless works of art at its heart.
Some sang hymns as they watched the important Catholic place of worship burn.
French President Emmanuel Macron has arrived at the scene where devastating footage earlier captured the moments the spire of one of Paris' most recognisable landmarks collapsing.
The leader has arrived to speak to emergency services as the world watches the cathedral burn, prompting messages of sorrow from around the world.
Moving footage has captured crowds singing Ave Maria as they watch Notre Dame burn.
The scenes prompted a message from the Vatican, which says the fire has caused "shock and sadness."
The Vatican says it is close to French Catholics and is keeping Paris firefighters in its prayers.
It issued a statement: "The Holy See has seen with shock and sadness the news of the terrible fire that has devastated the Cathedral of Notre Dame, symbol of Christianity in France and in the world."
Manchester United legend Gary Neville says he is HAPPY at the Red Devils' downturn in form - because it has shown all is not rosy at Old Trafford.
Ole Gunnar Solskjaer took his side on an incredible run of form after succeeding Jose Mourinho at the club in December.
It culminated in a dramatic comeback at the Parc des Princes as United upset the odds to dump Paris Saint-Germain out of the Champions League.
They were rewarded with a tie against Barcelona in the last eight, and once more have it all to do as they go to the Nou Camp looking to overturn a 1-0 deficit on Tuesday night.
But, despite four defeats in six games since their win in the French capital, Neville explained why United's struggles may actually be a good thing in the long term.
“It’s been a big struggle since the PSG game, and in some ways I am happy," he said on Sky Sports' Monday Night Football.
"Because if United had carried on as they were until the end of the season, it could have conned and fooled everyone into thinking this squad is OK.
“If there players are that susceptible to what you’re suggesting, that as soon as he [Solskjaer] gets the job they dip a little bit, he needs to know now.
“I’m actually not unhappy that Ole is now finding out more about these players in the last month than he did in the first six to eight weeks where everything was just golden.
“It was unbelievable the run that they went on. The PSG game was one of the best nights I’ve ever had as a United fan.
"It was crazy, mad, but felt so United in terms of the last 15 or 20 years, what we have always thought United are, coming back and achieving the unthinkable.
“All of a sudden, the last month or so, the reality has kicked in. They have started to show vulnerabilities and perform a little bit at times like they did earlier on in the season.
“I’m actually happy that they gave Ole the job, he has been able to see the players’ mentality in the last four or five weeks, there is still a lot to play for but I think he recognises now that there is a big job to do.
“What we saw earlier on in the season, we can’t just forget about. We can’t forget about that, I can’t forget about what I was watching.
“As much as I enjoyed watching it when Ole took over, now we’re seeing it settle down a bit. Ole wants to be in the job for two or three years, he’s going to need to get some different players around him and manipulate that squad."