French President Emmanuel Macron has said the opening ceremony for the Paris Olympics planned on the River Seine could be shifted instead to the Stade de France if the security threat is deemed too high.

Speaking to French media BFM-TV and RMC, Mr Macron said French law enforcement will be mobilised at an exceptional level for the security of the open-air event.

“But if we think there are risks, depending on our analysis of the context, we have fallback scenarios,” Mr Macron added.

“There are plan Bs and plan Cs.”

The July 26 event is set to be the first Olympic opening ceremony held outside a stadium setting.

Stade de France
There are contingency plans to hold the ceremony at the Stade de France should the security risk be too high (Anthony Devlin/PA)

About 10,500 athletes will parade through the heart of the French capital on boats on the Seine along a 3.7-mile route.

To limit security risks, Mr Macron said organisers could decide to shorten the itinerary of the parade on the Seine, and even to “repatriate the ceremony to the Stade de France” for a more conventional opening event.

Organisers had originally planned a grandiose opening ceremony for as many as 600,000 people, most watching free of charge from riverbanks.

But security and logistical concerns have led the government to progressively scale back its ambitions.

Earlier this year, the overall number of spectators was reduced to around 300,000.

The French government also decided that tourists will not be given free access to watch the opening ceremony because of security concerns.

Free access will be invitation-only instead.