The raids took place in the greater Paris region of Île-de-France and the Provence-Alpes-Côtes-d'Azur region of the south east.
According to reports some nine individuals aged between 18 and 60-years-old were arrested in the raids carried out by France's specialist counter-terrorist police.
The arrests were reportedly made in the Val-de-Marne department to the south west of Paris, Seine-Saint-Denis to the capital's north, the city of Aix-en Provence, north of Marseille and the town of Menton, on the border with Italy.
Those held included two brothers who were known to have been radicalised, sources told AFP.
An arrest was also made in Switzerland which brought the total number of suspects held to 10.
The 27-year-old man arrested in Switzerland was in contact with a 14-year-old French boy who was "about to carry out the attack," one of the sources said.
The teenager was arrested in the Paris region on June 20 and charged by an anti-terror judge, the sources said.
A photo of the boy holding a paper vowing his allegiance to the Islamic State group was found on social media, they added.
The Swiss man was "particularly active on social networks... and he had contacts with individuals living in France with whom he notably discussed
violent actions," a judicial source said.
According to BFM TV those arrested are suspected of planning and preparing a terror attack.
The suspects exchanged "disturbing remarks" on the Telegram encrypted messaging app, the sources said, adding that investigators were seeking to "determine what they were plotting".
It is not clear at this stage what their intentions were nor how far down the line their plans were, but according to Le Parisien newspaper, which first broke the news of the raids, the suspects planned to target the Riviera city of Nice, where 86 people were killed in the Bastille Day truck attack in 2016.
Quoting its own sources close to the probe Le Parisien said the intentions of the suspects had "become firm".
Authorities in France have not confirmed Nice was indeed the target.
France remains on high alert for terror attacks and last week the Minister of Interior Gerrard Collomb claimed that 32 attacks had been foiled since the State of Emergency was declared the night of the November 2015 shootings and bombing in Paris.