'No plan B' for Olympics opening ceremony after knife attack in Paris

"We have no plan B, we have a plan in which there are several sub-plans with a certain number of adjustment variables," Amelie Oudea-Castera told France Inter radio.

The 26-year-old suspect, a French national arrested after the attack, had pledged allegiance to Islamic State in a video recorded beforehand, anti-terrorism Prosecutor Jean-Francois Ricard said on Sunday.

The attack occurred on the Quai de Grenelle - a spot also included in the plans for the opening ceremony.

Asked if the government was mulling a change to its plan to hold the ceremony on the River Seine, with several hundred thousand spectators expected along its banks amid the security threats, the minister said: "This not something we're working with."

"We have the capacity to secure the event", she said, adding that certain details, including the number of additional cultural events surrounding the main spectacle and said the security perimeter would be adjusted closer to the Games.

France has been on high alert since raising its security threshold in October, when a Chechen-origin man with a knife killed a teacher in a school in northern France.

European security officials have warned of a growing risk of attacks by Islamist militants amid the Israel-Hamas war, with the biggest threat likely from "lone wolf" assailants who are hard to track.

Some 160 boats will set off on July 26 from the Pont d'Austerlitz for a six-kilometre journey to the Pont d'Iena in an event Tony Estanguet, the head of the organising committee, described as "unique and spectacular".