France foiled a plan to attack the country’s military, the interior minister said Wednesday, as a source close to the investigation said the suspects had been planning a beheading.

France foiled a plan to attack the country's military, the interior minister said Wednesday, as a source close to the investigation said the suspects had been planning a beheading.

Interior Minister Bernard Cazeneuve told reporters that four accused who had been planning "a terrorist act against French military facilities" were in custody of the country's intelligence services, the DGSI.

Aged 16 to 23 and including a former member of the navy, they were arrested at dawn in different parts of the country, the minister said.

The news of the arrests followed a statement from President Francois Hollande, who said attacks had been thwarted in recent days.

"This week, we stopped terrorist attacks which could have taken place," Hollande said on a visit to the coastal city of Marseille.

Cazeneuve said no link had been established between the foiled assault and two blasts on Tuesday at a petrochemical plant near Marseille.

A source close to the investigation into the thwarted attack, who asked to remain anonymous, said the four people arrested had been planning to film the decapitation of a member of the military.

One of four suspects, who was identified as the mastermind, had been planning to travel to extremist-controlled areas of Syria, Cazeneuve said.

Paris has tightened security around sensitive sites such as factories, calling for "maximum vigilance", after the Charlie Hebdo attacks in January where a trio of gunmen killed a total of 17 people starting with a massacre at the satirical magazine.