French Interior Minister Bernard Cazeneuve said the women aged 19 to 39 were arrested in connection to the discovery of a car filled six gas cylinders on Sunday, near the Notre Dame Cathedral.

They were “radicalized fanatics” preparing “imminent action.”

French police arrested three female suspects planning the attack on Thursday. One woman was shot during the standoff with the police in Boussy-Saint-Antoine, south of Paris.

A bar employee alerted authorities on Sunday after spotting a gas cylinder in a parked Peugeot 607 with no number plates and hazard lights flashing.

The cylinder was found empty, but six full ones were found in the back of the car. No detonators were found. However, documents in Arabic were found in the car.

Two brothers and their girlfriends have also been arrested on Wednesday and Thursday.

One of the couples arrested in southern France have long been under secret services surveillance. The 34-year-old man and the 29-year-old woman were involved with radical Islamic networks.

Notre Dame attracts 13 million visitors a year and may have been targeted to inflict maximum casualties.

French security forces are in high alert fearing there are now fighters returning from Syria that could be seeking to take their fight in Europe. It is estimated that up to 700 French nationals maybe still fighting in Syria.

(DW, Reuters, AP, AFP, France24)