Updated 1.03pm -

France will invite architects from around the world to submit designs for rebuilding the spire of Notre-Dame cathedral that was destroyed in a devastating blaze, Prime Minister Edouard Philippe said Wednesday.

The goal is "to give Notre-Dame a new spire that is adapted to the techniques and the challenges of our era," Philippe said at a press conference in Paris.

Precious rooster statue found

Meanwhile, a wrought copper statue of a rooster that sat atop the Notre-Dame spire has been found "battered" in the debris of the Paris cathedral.

The statue is considered all the more important because it contains three holy relics -- including a fragment of the Crown of Thorns believed by Christians to have been worn by Jesus Christ during his crucifixion, placed there to protect Parisians. 

The sculpture of the bird -- which is an unofficial symbol of France -- was recovered Tuesday by a restorer picking through the rubble left when the spire, on which it had sat, toppled at the height of the inferno that ravaged Notre-Dame on Monday, a ministry spokesman told AFP.

The head of the French Builders Federation, Jacques Chanut, posted a picture of the restorer holding a green-coloured rooster statue in the street.

The ministry spokesman said the statue had been handed over to religious officials, without elaborating.

A ministry official separately told Le Parisien newspaper that the statue was "battered but apparently restorable".

The official was quoted saying that, when the 19th-century spire had collapsed into the cathedral, the rooster statue had detached "and fallen on the good side... away from the seat of the fire".

Because of the statue's damage, it was not yet possible to verify if the Crown of Thorns fragment or the other relics were still inside, the official said.

In a stroke of good timing, sculptures of the Twelve Apostles and four New Testament evangelists that adorned the cathedral had been lifted off the building last week, before the fire, for restoration work in the southwestern city of Perigueux.

Those statues had been fixed to the cathedral in the mid-19th century when the spire had been built to replace the original 13th-century one that had been dismantled in the late 18th century because of weather damage.

Pope thanks Notre-Dame firefighters on behalf of whole Church

Pope Francis on Wednesday thanked the firefighters who risked their lives to save the Notre-Dame Cathedral in Paris on behalf of the entire Catholic Church.

"The gratitude of the whole Church goes to all those who did everything they could, even risking their lives, to save the Basilica," he said during the weekly general audience in Saint Peter's Square.

Francis said he had been "very saddened" by the vast blaze on Monday which gutted the great Paris landmark, destroying the roof, causing the steeple to collapse and leaving France reeling in shock.

A firefighter suffered injuries during the blaze, which at one point threatened to bring down one of the two monumental bell towers on the western facade of the cathedral that is visited by 13 million tourists each year.

The Holy Crown of Thorns, believed to have been worn by Jesus at his crucifixion, was saved by firefighters, as was a sacred tunic worn by 13th-century French king Louis IX.

Rescuers formed a human chain at the site of the disaster to evacuate as many artefacts as possible.

The bells of all cathedrals in France will sound at 6.50 pm on Wednesday, 48 hours after the fire started.