Twitter reacts to 'heartbreaking' and 'tragic' Notre Dame Cathedral fire

President Emmanuel Macron cancelled a speech to the nation and was on his way to the scene.

The cause of the blaze isn't yet known, but scaffolding could be seen on the roof of the burning structure.

"There will be nothing left", he said.

French historian Camille Pascal told BFM broadcast channel the fire was destroying "invaluable heritage".

Images taken by press photographers from the roof of the church just last week show the significant extent of the restoration work taking place on the almost 700-year old structure.

Paris police say fighters are inside the cathedral working to put the flames out while others work from the exterior.

Notre Dame is a functioning Catholic church and the site of many important religious and ceremonial events.

Its main rival as a national symbol, the Eiffel Tower, is little more than a century old. "We are sending all of our support and strength to the people of Paris-and stand ready to provide any and all resources we can".

It has given its name to one of the country's literary masterpieces.

"We are deeply saddened by the ongoing fire at the Notre-Dame cathedral", said a YouTube spokesman.

The last time the cathedral suffered major damage was during the French Revolution, when statues of saints were hacked by anti-clerical hotheads. "It's one of the great treasures of the world, the greatest artists in the world, probably, if you think about it, I would say it might be greater than nearly any museum in the world, and it's burning very badly, looks like it's burning to the ground".

German Chancellor Angela Merkel was among the first world leaders to offer her sympathies over the fire that overwhelmed the 12th century icon, saying "our thoughts are with our French friends".

Police in Paris told the public to clear the area so emergency vehicles and firefighters could access the building in the heart of the capital.

US President Donald Trump suggested "perhaps flying water tankers" could be used to extinguish the fire.

The cathedral was evacuated when the fire alarm was activated around 6.30pm, according to André Finot, a spokesman for Notre Dame.

The peak of the church is undergoing a 6 million-euro ($6.8 million) renovation project.

  • Marlene Weaver