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jihadists terroristsThinkstock

French authorities have foiled a plot by four would-be extremists to attack military bases, the interior minister said Wednesday, according to The Associated Press (AP).

The suspects, aged between 16 and 23, were arrested Monday at four separate locations around France, Interior Minister Bernard Cazeneuve said.

Cazeneuve said the group's leader had been under surveillance after his online activities raised investigators' suspicions. He had also triggered alarms by signaling his desire to travel to Syria, the interior minister added.

One of the suspects was a former member of the French navy, Cazeneuve said.

The minister said authorities break up similar plots every week in France, where more than 300 people have been implicated in jihadist activities since 2012.

There are no known links between the suspects arrested Monday and a double blast Tuesday at a petrochemical plant in southern France, Cazeneuve said, according to AP.

A total of 1,850 French citizens or permanent residents are implicated in jihadist networks, and 500 are believed to be currently in Syria or Iraq, the minister said.

The announcement of the foiled attack comes several weeks after Yassin Salhi, 35, beheaded his boss in an attack on a gas factory in Lyon during the Muslim month of Ramadan.

Salhi sent a gruesome selfie photo of himself and the severed head to a WhatsApp number in Canada after the attack. He was apprehended by security forces and later confessed to killing his boss.

The assault took place six months after 17 were killed in Islamist attacks in Paris that began with the Charlie Hebdo massacre.