A spire at the famous Notre-Dame Cathedral in Paris has collapsed amid a major fire at the 850-year-old building.
Paris streets were covered in smoke as one of the world’s iconic landmarks was partially destroyed.
Firefighters were desperately trying to save the church, with the blaze going for at least two hours. Tourists had been cleared of the building, one of the city’s major attractions besides the Eiffel Tower.
Horrified onlookers took to Twitter, posting videos of fire spewing from the top of the well-known landmark as police worked to keep them at a distance.
French newspaper Le Monde reported the fire started in the attic of the building and spread, causing the spire to collapse.
According to fire fighters on scene, the blaze could possibly be linked to restorations underway in the building with scaffolding visible in photos of the tragedy.
US President Donald Trump took to Twitter to share his shock.
“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!”
Others posted photos of the cathedral when they had visited in the past, lamenting the loss of the historic building which survived desecration during the French Revolution and was subject of Victor Hugo’s 1831 novel, The Hunchback of Notre-Dame.
French President Emmanuel Macron postponed a speech he was due to give on Monday evening (local time) about the measures he planned to take in response to the Yellow Jacket movement, which have staged protests for months on end.
“Notre-Dame de Paris in flames. Emotion of a whole nation,” Mr Macron tweeted.
“Thought for all Catholics and for all French. Like all our compatriots, I am sad tonight to see this part of us burn.”
A presidential official said Mr Macron was to go to the scene of the blaze.
A huge plume of smoke wafted across the city and ash fell over a large area. “Everything is collapsing,” a police officer near the scene said as the entire roof of the cathedral continued to burn. Firefighters cleared the area around the cathedral, which marks the very centre of Paris. Buildings around it were evacuated.
“A terrible fire is under way at Notre-Dame Cathedral in Paris,” Mayor Anne Hidalgo said on Twitter.
“The Paris fire service is trying to control the flames,” she wrote, asking residents to respect the security cordon thrown up around the site.
A spokesman for the cathedral told reporters that the wooden structure supporting the roof was being gutted by the blaze.
The fire service said the blaze could be “potentially linked” to ongoing renovations.
A spokesman for the cathedral said the fire, which comes as French Catholics prepare to celebrate Easter, broke out at around 4.50pm (12.50am AEST).
Fire trucks could be seen speeding through Paris towards the scene on the Ile de la Cite — an island in the Seine at the heart of Paris.
The Paris police department in a tweet called on residents to avoid the area and to “make way for rescue vehicles”.
Hundreds of people gathered on the bridges of Paris downriver to witness the scene, some filming the images with their smartphones, an AFP reporter said.
A burning smell filled the air.
The French-Gothic cathedral hosts more than 50,000 visitors on peak-days and is home to a collection of paintings and sculptures and famed stained glass rose windows which have reportedly blown out in the blaze.
The cathedral has been world heritage-listed since 1991.
Notre-Dame was in the midst of renovations, with some sections under scaffolding and bronze statues were removed last week for works.