A major fire has engulfed the medieval cathedral of Notre-Dame in Paris, one of France's most famous landmarks, according to French fire services.

The flames have broken out at the building on Monday evening, April 15, 2019, at around 18:30 (16:30 GMT) and quickly devastating the spire and roof, sending plumes of black smoke into the sky and seriously injuring a firefighter, Sky News English stated.

"I am so sad tonight to see this part of all of us burn," the French President Emmanuel Macron said, declaring a national emergency.

President Macron also expressed sympathy with Catholics all around the world following the tragedy, adding that the worst had been avoided.

President Macron vowed to launch an international fundraising campaign to help rebuild Notre-Dame.

France's interior minister has earlier warned that the 400 firefighters scrambled to the scene may not be able to save the cathedral, as the fire was massive; however, after more than four hours, the main structure had been "saved and preserved" from total destruction.

"Thoughts are with the people of France tonight and with the emergency services who are fighting the terrible blaze," the British Prime Minister Theresa May said.

Eyewitnesses filmed a video showing the moment the historic landmark's steeple was consumed by flames before toppling over.

"Hours later the area where the spire had once been was still burning with sparks falling from the cathedral's vaulted ceiling," Sky News English said.

An eyewitness described people "howling and gasping" as they watched the destruction unfold.

Paris mayor Anne Hidalgo urged the public to respect the security perimeter around the scene while firefighters tackled the terrible blaze, stressing that the areas close to the scene were evacuated.

A firefighter at the scene confirmed that firefighters spent all efforts on saving the artwork at the back of the cathedral and stopping the northern tower from collapsing.

Paris prosecutors have opened an investigation into the fire, ruling out arson or possible terror-related motives and instead they thought the blaze was started by accident.

Former US president Barack Obama also wrote on his Twitter account: 

Notre Dame is one of the world’s great treasures, and we’re thinking of the people of France in your time of grief. It’s in our nature to mourn when we see history lost – but it’s also in our nature to rebuild for tomorrow, as strong as we can. pic.twitter.com/SpMEvv1BzB

— Barack Obama (@BarackObama) April 15, 2019

The Vatican, the head of the Catholic Church, said it was praying for French firefighters.
The cathedral is over 800 years and is famous for featuring in Victor Hugo's classic novel the Hunchback of Notre-Dame.

The building was in the midst of renovations, with some sections under scaffolding, while bronze statues were removed last week for works.

It is visited by millions of tourists every year and is translated into English as "Our Lady."

Construction continued for much of the next century, with major restoration and additions made in the 17th and 18th century.

The 387 steps up to the towers take visitors past the gallery of chimeras, mythical creatures typically composed of more than one animal.