French President Emmanuel Macron has set an ambitious target for the rebuilding of Notre-Dame Cathedral after it was nearly destroyed by fire on Monday.

The fire caused extensive damage to the 850-year-old building, including the collapse of its roof and spire.  But some 500 firefighters worked together to save the main stone structure, including the famous twin bell towers. 

The full extent of the damage will be known once experts are allowed access to the building after it has been stabilised. 

President Macron has extended an invitation to the world to donate towards the reconstruction of the iconic building, France's most visited landmark. 

French billionnaires are leading the way, with luxury companies the LVMH Group, Kering and L'Oreal on Tuesday pledging a combined €500 million towards the rebuilding effort. LVMH is the parent group behind brands like Louis Vitton and Christian Dior, while Kering owns Gucci and Yves Saint Lauren. 

President Macron said he wanted to see Notre-Dame rebuilt in five years - in time for the Paris Summer Olympics in 2024.

"We'll rebuild Notre-Dame even more beautifully and I want it to be completed in five years, we can do it," said Mr Macron.

"It's up to us to convert this disaster into an opportunity to come together... It's up to us to find the thread of our national project."

An investigation into the cause of the blaze is in the early stages but arson has already been ruled out and the Paris prosecutors' office has said that police will be carrying out an investigation into "involuntary destruction caused by fire". 

The scale of the devastation was met with an outpouring of grief from people all around the world.  In France, the Catholic Church said it was a "shock far beyond our country's Catholics". 

On Wednesday, bells at cathedrals across France were to ring out in solidarity with the people of Paris. 

The Archdiocese of Paris expressed its thanks for the messages of support it has received from around the world. 

"France cries and with her all her friends from all over the world. She is touched to the heart because her stones are the testimony of an invincible hope which, by the talent, the courage, the genius and the faith of the builders, raised this luminous lace of stones, wood and glass," it said.

"This faith remains ours. It is she who moves the mountains and we will rebuild this masterpiece.

"Dear brothers and sisters, dear friends, thank you for all the many signs of friendship and encouragement that come from everywhere.

"Thank you for the outpouring of solidarity, thank you for the fervent prayer that consoles our heart. Let us take advantage of this emotion so great to live intensely during this week that is so decisive for Christians."