EPIC BATTLE: Firefighters save iconic Notre Dame towers

Fire broke out at 6pm local time
Authorities 'optimistic' towers can be saved
Dramatic footage shows spire collapsing
Parisians gather to sing for 'fallen cathedral'

Parisian firefighters have fought and won an almighty battle to preserve iconic Notre-Dame Cathedral, after it was engulfed in a catastrophic fire,

Although the inferno was still burning more than five hours after it erupted, authorities were optimistic they had salvaged the building's main towers.

"We can consider that the main structure of Notre-Dame has been saved and preserved," Paris fire brigade chief Jean-Claude Gallet told reporters outside the cathedral.

But the massive fire that consumed the cathedral had already destroyed the spire and the roof of the historic Paris landmark.

The Paris prosecutors' office ruled out arson and possible terror-related motives, and said it was treating it as an accident.

Emmanuel Macron vowed that France "will rebuild Notre-Dame".

The French President was emotional as he said, "Notre-Dame is at the epicentre of our lives.

The Cathedral of all of France even if they've never been. But it is burning and I know that there is sadness."

French billionaire Francois-Henri Pinault - who is married to actress Salma Hayek - pledged 100 million euros ($A157 million) towards the rebuilding.

In a statement sent to AFP the CEO of the Kering group, which owns Gucci and Yves Saint Laurent fashion houses, said the money towards "the effort necessary to completely rebuild Notre-Dame" would be paid by the Pinault family's investment firm Artemis.

TOURISTS SHOCKED BY FIRE

Sydneysiders Lee Holmes, 51, and Georgie Bridge, 52, were taking photographs near the famous cathedral moments before it caught fire.

They were shocked no-one was killed as flames engulfed the historic building.

"It was 6.50pm (local time) and were in front of the cathedral, looking directly at this plume of smoke," Ms Holmes said.

"By 7pm it was raging."

Ms Bridge added: "I'm surprised no one got hurt, there would have been easily 1000 people in there or more."

Smoke billowing from Notre Dame as the fire takes hold. Picture: Supplied
They said that there were people holding their hands over their mouths in disbelief at the sight.

And then groups of people began singing hymns in French, as they mourned the loss of more than 800 years of history.

"There was a lady singing a hymn, I'm not sure of the name but they were singing 'holy Mary mother of god, pray for us sinners' over and over again," Ms Holmes said.

Flames that began around 6pm local time (2am AEST) burst rapidly through the roof of the centuries-old cathedral and engulfed the spire, which collapsed, quickly followed by the entire roof.

MORRISON SAYS PARIS 'WILL REBUILD'

Australian Prime Minister Scott Morrison said Parisians will rebuild in the aftermath of the devastating blaze.

Both the prime minister and Opposition Leader Bill Shorten expressed their sadness over the blaze.

"I fondly remember standing outside Notre Dame with Jen almost 30 years ago. So sad to see this beautiful cathedral in flames this morning," Mr Morrison tweeted on Tuesday.

"Our thoughts are with the people of France and emergency services who are fighting this fire. They will rebuild as Parisians always do."

Mr Shorten said it was a sad day for Paris, France and people across the world. "Notre Dame brought so much joy to so many souls," he wrote on Twitter.

Former prime minister Malcolm Turnbull also expressed his sympathies, and called on both his successor and Mr Shorten to establish a fund to support the restoration of the church.

He said he has no doubt French President Emmanuel Macron will ensure the cathedral is restored.

International leaders shared their shock and sadness over the incident.

FLAMES SHOT UP INTO THE AIR

At the height of the blaze, flames reached one of Notre Dame's towers and brought down the building's 96-metre spire.

A huge plume of smoke wafted across the city and ash fell over a large area. Parisians watching from the other side of the River Seine gasped as the spire folded over on to itself and fell into the inferno.

Firefighters battled the blaze with water hoses and cleared the area around Notre-Dame. Tourists were evacuated from nearby hotels.

Witnesses said the whole island on which the building stands, the Ile de la Cite, was evacuated.

"Everything is collapsing," a police officer near the scene said as the cathedral continued to burn.

During the fight to save the structure, the French Civil Security service - possibly responding to US President Donald Trump's suggestion that firefighters "act quickly" and employ flying water tankers - said that was not an option as it might destroy the entire building.

"Helicopter or plane, the weight of the water and the intensity of dropping it at low altitude could weaken the structure of Notre-Dame and cause collateral damage to surrounding buildings," it tweeted.

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 firefighters on the scene, the blaze could possibly be linked to restorations underway in the building with scaffolding visible in photos of the tragedy.

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 the setting of Victor Hugo's 1831 novel, The Hunchback of Notre-Dame.

Earlier, Mayor Anne Hidalgo said "a terrible fire" had broken out at the cathedral.

"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 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.

VATICAN 'DEVASTATED' BY BLAZE

The Vatican issued a statement, saying: "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."

The statement says the Vatican is praying for firefighters "and those who are doing everything possible to confront this dramatic situation" on Monday.

It also expressed "our closeness to French Catholics and the population of Paris, and we assure our prayers for firefighters".