French police detained three women believed to be planning an imminent terror attack in an operation south of Paris Thursday evening, the country's interior minister said. 

The discovery of the mysterious car has revived worries about the threat of new attacks in France, which has already repeatedly been targeted by Islamic State (ISIS) extremists and remains under a state of emergency. Seven people are now in custody in the Notre Dame case.

The three women were detained in Boussy-Saint-Antoine in a "veritable race against the clock," Interior Minister Bernard Cazeneuve told reporters. One of the women attacked police, and an intelligence officer was hospitalized with a knife wound to the shoulder. One suspect was also injured, Cazeneuve said.

"These radicalized, fanatic women, aged 39, 23 and 19 years old, were likely preparing new violent actions, particularly imminent," he said. "France is confronted with a terrorist threat of unprecedented scale. ... It requires the vigilance of all our compatriots."

The 19-year-old is the daughter of the owner of the abandoned car, according to two officials who were not authorized to be publicly named discussing an ongoing operation.

The car's owner went to police to report that his radicalized daughter was missing. He was briefly detained and then released.

Paris Prosecutor François Molins said in an interview with Le Monde newspaper last week that an increasing number of teenage girls have been radicalized, some with "terrorist plans."

Prosecutors opened a terrorist investigation after the car was found near the famous cathedral on Sunday morning. No one was inside, but police found five canisters filled with gas in the trunk and an empty canister on one of the seats. Along with the canisters, there were three jerry cans of diesel and papers with Arabic writing inside the vehicle.

No detonators were found in the car, which had been left on a narrow cobbled street in the popular Latin Quarter next to bars and restaurants.

Earlier, the Paris prosecutor's office said that police arrested a couple - a 27-year-old man and a 26-year-old woman - Wednesday in the Loiret region of France, south of Paris.

A second couple - a 34-year-old man and a 29-year-old woman - was detained in the same case on Tuesday.

The two men, who are brothers, and the two women were transferred to Paris to be questioned by investigators trained in counterterrorism. The prosecutor's office said all four are suspected of links to "radical Islamism."

Authorities are allowed to hold terror suspects for up to four days without charges.

The two arrested couples have been living in the Loiret region, in the area of Montargis town. In March, three members of a family were arrested in the same area on suspicion of being members of a terrorist network.

The Notre Dame case has revived memories of bombings across Paris in the 1990s by Algerian extremists, several of which involved gas canisters filled with nails.

The Associated Press contributed to this report.