Firefighters arriving at the Elysee Palace to meet French President Emmanuel Macron. - AFP/VNA Photo

PARIS – French President Emmanuel Macron on Thursday hailed as "exemplary" hundreds of firefighters who saved Notre-Dame in the devastating blaze, as efforts intensified to shore up the still fragile cathedral.

Some 600 firefighters worked throughout the night Monday to put out the fire at the Paris landmark and prevent an even worse disaster, in a blaze that felled the spire and destroyed two-thirds of its roof.

A prayer vigil was held at another of Paris's landmark churches, the Sacre-Coeur (Sacred Heart), on Thursday which was due to remain open all night.

One woman, Tanuja Saint Andre, 46, called Notre-Dame her "second home" and said she had prayed for "the Virgin Mary, for Notre-Dame and that the foundations hold".

Sixty firefighters are still maintaining a presence at Notre-Dame to ensure no further fire erupts while France's culture minister warned that two gables and figurines perched high up in the building were still at risk of collapse inside.

"The country and the entire world were watching us and you were exemplary," Macron told some 250 of the firefighters at the Elysee Palace. "You were the perfect example of what we should be," he added.

He said the firefighters would be awarded France's golden medal of honour in recognition of their "courage and devotion".

'Saved part of ourselves'

Mayor of Paris Anne Hidalgo also paid tribute to the firefighters and others who helped rescue the 850-year-old gothic masterpiece, in a public ceremony outside Paris city hall.

"You saved part of ourselves," she said, hailing the "boundless courage" of the firefighters who were loudly cheered by the assembled public as they took to the stage.

"It was 9:30 pm. The wind was blowing... There were flames around the northern bell tower with a temperature of 800 degrees," Interior Minister Christophe Castaner said in his tribute.

"Waiting even seconds more could have meant the tower and the facade fell. But they continued... risking their lives to save Notre-Dame. Only their mission counted," he said.

Culture Minister Franck Riester said on Thursday that even three days after the fire there remained concerns that parts of the building could collapse.

He said one gable in the north transept and another between the two great bell towers were at risk.

He also said that figures in the southern bell tower still risked falling and, if they did, this would damage the organs below. An operation will be undertaken to remove them.

But he added that "thanks to the exceptional work of the fire brigade, their courage, the strategy for attacking the fire adopted by the two officers in charge, we can say that the worst was avoided".

Macron had on Tuesday in an address to the nation outlined an ambitious strategy to rebuild Notre Dame within just five years, hailing the French as a nation of "builders".

The goal was warmly applauded by some but greeted with scepticism by some experts who warned of the painstaking work and expertise needed to make the cathedral anew.

Macron named former French chief of staff General Jean-Louis Georgelin his special representative for the reconstruction effort, who described his task as a "combat mission".

The president "has set an objective – five years. I need to make sure that everyone engaged in this battle mobilises to reach the objective," Georgelin told AFP.

Investigators trying to determine the cause of the blaze are questioning workers who were renovating the steeple, an operation suspected of accidentally triggering the blaze.

For the toppled spire, Prime Minister Edouard Philippe said on Wednesday that an international contest of architects would determine one of three options: not replacing the spire, rebuilding it as it was or creating a wholly new edifice.

'Extraordinary generosity'

Pledges of donations for rebuilding from France's biggest family companies, listed firms as well as foreign giants like Apple and Walt Disney have rolled in.

More than 850 million euros ($960 million) has now been pledged but there has been controversy over why the money has been so quick to come when France is beset by social problems.

"In one click, 200 million, 100 million. That shows the inequality which we regularly denounce in this country," the head of the CGT trade union, Philippe Martinez, said on Wednesday.

Riester however called the debate "pointless" and urged people to let this "extraordinary show of generosity to run is course".

Diplomatic sources said Thursday a former French ambassador to Russia and the Vatican, Stanislas de Laboulaye, 72, would be named as coordinator of the international aid effort.

Police in Paris said late Thursday that yellow vest protesters would be banned from the area around Notre-Dame on Saturday during their 23rd consecutive weekly protest against social inequality. – AFP