French President Emmanuel Macron has vowed that the cathedral of Notre-Dame will be rebuilt after fire ravaged the building on Monday night.

The spire and roof collapsed in the blaze that has stunned the world, but firefighters were able to save the main stone structure of the building, including its iconic two main towers. 

The fire was under control by Tuesday morning, officials said, and an investigation is underway to determine the cause. 

General Jean-Claude Gallet, commander of the Paris fire brigade, said: "We can consider that the two towers have been saved. The structure of Notre Dame is saved and preserved in its totality. Firefighters are going to work all night to save the artworks."

Mr Macron was at the site on Monday night where he met with police and fire chiefs.  He said the blaze was a "terrible tragedy" but added that the "worst had been avoided" and that a major global fundraising initiative would commence to rebuild the 12th century cathedral, a Unesco World Heritage site. 

 "We'll rebuild this cathedral all together and it's undoubtedly part of the French destiny and the project we'll have for the coming years," the president said, visibly emotional.

"That's what the French expect [and] because it's what our history deserves. Because it is our profound destiny ... it has witnessed all our major moments, our epidemics, our wars, our liberations. It is the epicentre of our lives."

As the fire spread through the building on Monday night, crowds of people gathered in the streets of Paris to watch, some in tears.  Others collected in groups to sing hymns and say prayers, while some churches around the city rang their bells in solidarity. 

Around 500 firefighters battled through the night to save the building - France's most visited landmark.  One was reportedly seriously injured. 

The medieval timber frame of the roof was lost, as were many of the stained glass windows. 

Extensive scaffolding surrounded the building at the time as it was undergoing major renovations.  It is not yet clear if the renovation works were a factor in the fire.

In the midst of the devastation, there were stories of hope.  Just last week, 16 copper statues were removed from the roof as part of the renovation works and emergency teams were able to rescue some of the priceless artworks and religious items stored inside the cathedral, including a crown of thorns said to be the one worn by Jesus before his crucifixion and a tunic worn by King Louis IX when he brought the crown of thorns to Paris, Archpriest of Notre-Dame Monsignor Patrick Chauvet told reporters.

Mgr Chauvet admitted he was "very upset" after the fire.

"This building is 850-year-old. To see the building fall to pieces, the spire fall down, just as we were renovating it ... All I can do is pray," he said.

The devastation caused to the landmark building has triggered an outpouring of grief around the world.  British Prime Minister Theresa May said her thoughts were with the people of France after the "terrible" blaze, whlie German Chancellor Angela Merkel described the cathedral as a "symbol of France and our European culture". 

The Queen said in a statement: "Prince Philip and I have been deeply saddened to see the images of the fire which has engulfed Notre-Dame Cathedral." 

The Vatican said the cathedral was a "symbol of Christianity in France and in the world" and that the fire had caused "shock and sadness".

The Bishops' Conference of France spoke of its "immense sadness" but asked people to look to Christ as the "source of our hope".

"They are well aware that the influence of Notre-Dame de Paris goes beyond the capital and that it will remain a major symbol of the Catholic faith and a place where all, believers and unbelievers, can meet at important moments of the history of our country," a statement read.