PARIS — Notre Dame Cathedral, the iconic symbol of the beauty and history of Paris, was scarred by an extensive fire Monday evening that caused its delicate spire to collapse, bruised the Parisian skies with smoke and further disheartened a city already back on its heels after weeks of violent protests.

The spectacle of flames leaping from the cathedral’s wooden roof — its spire glowing red then turning into a virtual cinder — stunned thousands of onlookers who gathered along the banks of the Seine and packed into the plaza of the nearby Hôtel de Ville, gasping and covering their mouths in horror and wiping away tears.

“It is like losing a member of one’s own family,” said Pierre Guillaume Bonnet, a 45-year-old marketing director.

“For me there are so many memories tied up in it,” he said of the cathedral.

Around 500 firefighters battled the blaze for nearly five hours. By 11 p.m. Paris time, the structure had been “saved and preserved as a whole,” the fire chief, Jean-Claude Gallet, said. The two magnificent towers soaring above the skyline had been spared, he said, but two-thirds of the roof was destroyed.

“The worst has been avoided even though the battle is not completely won,” President Emmanuel Macron said in a brief and solemn speech at Notre Dame on Monday night, vowing that the cathedral would be rebuilt.

“This is the place where we have lived all of our great moments, the epicenter of our lives,” he said. “It is the cathedral of all the French.”

The fire broke out about 6:30 p.m., upending Macron’s plans to deliver an important policy speech about trying to heal the country from months of demonstrations by the yellow vest protest movement that had already defaced major landmarks in the capital and disfigured some of its richest streets.

The tragedy seemed to underscore the challenges heaped before his administration, which has struggled to reconcile the formidable weight of France’s ideals and storied past with the necessity for change to meet the demands of the 21st century.

The cause of the fire was not immediately known, officials said. No one was killed, they said, but a firefighter was seriously injured.

A jewel of medieval Gothic architecture built in the 12th and 13th centuries, Notre Dame is a landmark not only for Paris, where it squats firmly yet gracefully at its very center, but for all the world. The cathedral is visited by about 30,000 people a day and around 13 million people a year.

For centuries France’s kings and queens were married and buried there. Napoleon was crowned emperor in Notre Dame in 1804, and the joyous thanksgiving ceremony after the Liberation of Paris in 1944 took place there, led by Charles de Gaulle.

World leaders congregated at the cathedral in a memorial service for de Gaulle in 1970, and then again for President François Mitterrand in 1996.

On Monday evening, as the last rush of tourists were trying to get in for the day, the doors of Notre Dame were abruptly shut without explanation, witnesses said.

Within moments, tiny bits of white smoke started rising from the spire — which, at 295 feet, was the highest part of the cathedral.

Billowing out, the smoke started turning gray, then black, making it clear that a fire was growing inside the cathedral, which is currently covered in scaffolding. Soon, orange flames began punching out of the spire, quickly increasing in intensity.

French police rushed in and started blowing whistles, telling everyone to move back, witnesses said. By then, the flames were towering, spilling out of multiple parts of the cathedral. Tourists and residents alike came to a standstill, pulling out their phones to call their loved ones. Older Parisians began to cry, lamenting how their national treasure was quickly being lost.

Thousands stood on the banks of the Seine river and watched in shock as the fire tore through the cathedral’s wooden roof and brought down the spire. Video filmed by onlookers and shared on social media showed smoke and flames billowing from the top of the cathedral.

The cathedral’s rector, Monsignor Patrick Chauvet, said firefighters were able to save some of the cathedral’s artworks but did not say how much was damaged inside the building. A linen fabric associated with Saint Louis, the Holy Crown of thorns and the cathedral’s treasury were saved.

Gallet, the fire chief, said firefighters were still rescuing artworks in the building, hours after the fire had started. The main risk, he said, was the smoke within the cathedral, and the fall of materials, including melting lead.

The cathedral had been undergoing extensive renovation work. Last week, 16 copper statues representing the Twelve Apostles and four evangelists were lifted with a crane so that the spire could be renovated.

In recent years, the Friends of Notre Dame, a foundation based in the United States, estimated that the structure needed nearly $40 million for urgent repairs. The French state, which owns the cathedral, already devotes up to 2 million euros (about $2.4 million) a year in upkeep.

In a statement, San Antonio Archbishop Gustavo Garcia-Siller said he was praying for “consolation from God for the people of Paris and all of France as they cope with shock and profound sadness,” adding, “We in the Archdiocese of San Antonio pray especially at this time for the safety of firefighters and first responders battling this enormous fire.”