The Olympic flame is set to arrive in the French port of Marseille on Wednesday in front of a crowd of up to 150,000 people in a first major test of the hugely ambitious plans for the Paris Games.

The transfer of the flame onshore from a 19th-century tall ship will mark the start of a 12,000-kilometre (7,500-mile) torch relay across mainland France and the country's far-flung overseas territories.

Organisers are hoping the first public spectacle of their much-hyped "iconic" Olympics - just 79 days away - will help build excitement after a damaging row about ticket prices and ongoing concerns about security.

"It's something we've been waiting for for a very long time," chief organiser Tony Estanguet told reporters on Monday. "It's here. One hundred years after the last Games, the Games are coming home."

When the Paris opening ceremony begins on July 26, it will be the first time the city has played host for a century after previous editions in 1924 and 1900.

France sees itself at the heart of the modern Olympic movement after a French aristocrat, Pierre de Coubertin, revived the idea of the Games as practised by the Greeks until the 4th century BC.

After the Covid-hit edition in Tokyo in 2021 and the corruption-tainted Rio de Janeiro version in 2016, the Paris Olympics are seen as an important moment for the sporting extravaganza as a whole.

A measure of public excitement will come when the flame is handed over on Wednesday evening from the Belem, a historic French trade vessel that has made a 12-day trip from Greece.

"We are going to do beautiful, grandiose, sober and accessible at the same time," Marseille mayor Benoit Payan promised to AFP ahead of the flame arriving, while recalling how his gritty port city was founded by Greek traders in 600 BC.

- 'Beautiful, grandiose' - Over 1,000 other boats will accompany its approach to the harbour and organisers expect around 150,000 people to witness the transfer in the revamped marina of Marseille, which will host the sailing events during the Olympics.

Fireworks and a free concert will complete the show which will be broadcast live on French TV.

In the background, around 6,000 members of the security forces are expected to be on duty in a major test of the vast security plans put in place at a time when the country is on its highest terror alert.

"It's completely unprecedented for the national police to mobilise so many people on the same day at the same place," regional police coordinator Cedric Esson told reporters on Monday.

The honour of being the first torch bearer will fall to four-time Olympic medal-winning swimmer Florent Manadou.

Other stars scheduled to take part in the parade, which continues on Thursday, include NBA-winning basketball player Tony Parker and footballer Didier Drogba, as well as charity and entertainment figures.

One beach-cleaning charity has boycotted it to protest Olympics sponsor Coca-Cola, while there is no scheduled against role for Marseille's most famous sporting son, football legend Zinedine Zidane.

- Opening ceremony - Extremely tight security will be a constant feature as the torch travels through more than 450 French towns and cities, and passes by dozens of tourist attractions including the Mont Saint Michel.

Around 200 security forces are set to be positioned permanently around it, including an anti-terror SWAT team and anti-drone operatives.

Interior Minister Gerald Darmanin has referred to the risk of protests, including from far-left groups or environmental activists such as Extinction Rebellion.

Organisers have promised a "spectacular" and "iconic" Olympics, with much of the sport set to take place in temporary venues around the City of Light including at the Eiffel Tower and the Invalides.

In the absence of a much-feared security scare, the opening ceremony will take place in boats on the river Seine in a radical departure from past Games which have opened in the main stadium.

All of the major infrastructure has been completed with only two new permanent sporting venues built in a bid to reduce the financial cost and carbon emissions of the global extravaganza.

The idea of the torch rally harks back to the ancient Olympics when a sacred flame burned throughout the Games.

The Paris Olympics will run from July 26-August 11, followed by the Paralympics from August 28-September 8.