French President Emmanuel Macron says Notre-Dame cathedral will be rebuilt “even more beautifully” – and that he wants the work done within five years.
A massive fire on Monday ravaged the 850-year-old Gothic building, destroying much of its roof and causing its steeple to collapse.
The cathedral was minutes away from total destruction, officials say.
But despite Mr Macron’s pledge experts say its reconstruction could take decades.
Fifty people will investigate the cause of the fire. Paris public prosecutor Rémy Heitz said there was no obvious indication of arson and that the blaze was being treated as an accident.
A combined €800m ($902m; £692m) has already been pledged by a number of companies and business tycoons to help rebuild the Unesco World Heritage site.