An intense fire has broken out at the 19th Century basilica of Saint-Donatien in the city of Nantes in western France.
The fire broke out on Monday after morning Mass, with worshippers evacuated from the building, Rev Benoit Bertrand told local media.
Around 40 firefighters worked to extinguish the flames, which are believed to have originated on the roof where work was being carried out.
Two workers escaped from the top of the building unharmed.
The Mayor of Nantes Johanna Rolland said the basilica was “an important symbol” for the Catholic community.
In a statement on Facebook Johanna Rolland also thanked firefighters for their “rapid and brave action”.
The blaze broke out at around 10:30 local time and may have been linked to “waterproofing work”, according to the city’s chief fire officer.
The roof has been severely damaged and efforts are now underway to save several precious objects inside the basilica, most notably its organ.
Social media users shared images of the burning building on Twitter, showing smoke billowing from its rooftop.
The basilica dates back to the 19th Century and is dedicated to the religious martyrs St Donatien and St Rogatien.
VIDEO La Roche-Sur-Yon officials have banned a nativity scene, in the latest row over France’s secular traditions.
A judge in Nantes ruled that it was a “religious emblem” and incompatible with the French principle of “religious neutrality in public spaces”.
Town officials have reluctantly removed a figure of baby Jesus, plaster animals and a desk-sized stable they had erected in the local council building.
A local senator denounced the ruling.
France’s strict secularism laws mean that religious symbols are banned from public spaces such as schools, hospitals and local councils.
Secularism was a founding principle of the French Republic and was enshrined in a 1905 law separating Church and State.
“This decision is grotesque,” said Senator Bruno Retailleau in a statement. “Next we’ll be banning epiphany cakes at the Elysee Palace.”
Bruno Retailleau also argued that it was unfair as in Paris the mayor hosted a dinner celebrating the Muslim month of Ramadan every year.
Jean Regourd, a member of the secular Free Thinking Society, lodged the complaint against the nativity scene but denied attacking a tradition that is now part of secular French culture.
“It’s a child in a stable with a cow and a donkey,” he said. “It is clearly a religious symbol, there’s no doubt about it. And these local council buildings were built in the 1980s so there is no local nativity tradition to speak of.”
Bruno Retailleau has said he will appeal against the ruling but admits that keeping the nativity on display would be an “illegal act of civil disobedience”.