"Pray," the archbishop told the priests of Paris, he also invited them to ring church bells as a public invitation to prayer.
Unconfirmed reports indicate that the major religious and artistic treasures of the cathedral were removed as the fire began, including a relic of the crown of thorns.
As flames spread, locals reported buring debris from the fire falling in the immeadite vicinity of the cathedral. By 9pm the fire was contained within the cathedral building itself.
Firefighters cautioned Monday night that although the height of the flames had abated, the fire within the cathedral itself was not yet fully under contol. Efforts were initially hampered by the height of the cathedral roof, which prevented emergency services from reaching the flames.
No announcement has yet been made concerning any injuries or fatalities resulting from the fire.
Paris mayor Anne Hidalgo issued a series of brief statements via Twitter saying that emergency responders are fighting to control the flames and appealing to local residents to keep the area clear to assist their efforts.
"There is no word strong enough to express my sorrow," Hidalgo said.
Outside the security cordon, Parisian Catholics have gathered in large crowds, kneeling to pray and singing devotional hyms to Our Lady.
Officials have not yet determined what caused the fire, which is still burning. Both the fire department and the office of the public prosecuter in Paris have confirmed that invesitgations into the origin and cause of the fire have been opened.
Built between the twelfth through fourteenth centuries, the landmark cathedral in the French capital is one of the most recognizable churches in the world, receiving more than 12 million visitors each year.
The cathedral was undergoing some restorative work at the time the fire broke out, though it is unknown if the fire originated in the area of the work.
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The fire comes after several weeks of vandalism and arson attacks on church buildings across France.
Cardinal Daniel DiNardo, president of the U.S. bishops' conference released a statement on behalf of the American hierarchy calling the fire "horrific."
"This particular cathedral is not only a majestic Church, it is also a world treasure. Noble in architecture and art, it has long been a symbol of the transcendent human spirit as well as our longing for God," DiNardo said.
"Our hearts go out to the archbishop and the people of Paris, and we pray for all the people of France, entrusting all to the prayers and intercession of the Mother of God, especially the firefighters battling the fire."
This is a developing story and is being updated.