French police have arrested the boyfriend of one of three women held over the discovery of a car laden with gas cylinders in Paris, sources close to the probe said Friday.

The man, arrested late Thursday, was known to intelligence services for links to radical Islam, the sources said.

His brother is in custody over suspected links to Larossi Abballa, a jihadist who killed a police officer and his girlfriend in a Paris suburb in June, the sources said.

Three female suspects in the probe into the car found near Notre Dame cathedral in central Paris were also arrested Thursday, with Interior Minister Bernard Cazeneuve saying they were believed to be preparing attacks.

One of the women, a daughter of the car's owner, was reportedly shot and injured during the arrest.

She had pledged allegiance to the Islamic State group in a letter, according to a source close to the investigation.

A police source said security services had issued a warning Thursday about a possible attack on train stations in Paris and the suburb where the women lived.

Four people -- two brothers and their girlfriends -- were already in custody over the car, found just a few hundred metres (yards) from the Notre Dame cathedral, an area always thronged with tourists.