A total of 326,000 tickets are set to be sold or given away for the opening ceremony of the Paris Olympics on the river Seine, Interior Minister Gerald Darmanin said Tuesday, giving the exact number for the first time.

Organisers have scaled back their plans for the waterborne parade – with crowds once imagined as large as two million people – in the face of resistance from French security services and worries about terror attacks.

But it is still set to break records in terms of size, with all previous opening ceremonies taking place in the main athletics' stadium.

"We will have 104,000 spectators on the lower bank who have paid for a ticket," Darmanin told a hearing in the Senate. "Then you have 222,000 people on the higher banks [with free tickets]."

He estimated that another 200,000 people would watch the open-air parade on July 26 along the river from buildings that overlook the Seine, with an additional 50,000 in fanzones in the capital.

The open-air ceremony on boats is in keeping with promises to make the Paris Olympics "iconic", with the local organising committee keen to break from past traditions in the way it stages the world's biggest sporting event.

The 2008 Beijing Summer Olympics ceremony is generally considered to be the most spectacular in history while the 2012 London ceremony, overseen by "Trainspotting" director Danny Boyle, won rave reviews for showcasing Britain's quirky side.

A total of 180 boats are set to sail around six kilometres down the Seine, of which 94 will contain athletes, the top security official for the Paris region, Marc Guillaume, told the same hearing.

"No country has informed us that they do not want to take part," Darmanin explained. "They have confidence in our organisation."

The executive in charge of planning and risk management at the Paris organising committee told AFP last week that special security measures would be considered for high-risk delegations such as those from the US or Israel.

"Every delegation has its own unique circumstances, and we'll look at solutions that are adapted to the risk," Lambis Konstantinidis said. (AFP)