A 15-year-old boy has been arrested in Paris suspected of preparing imminent "violent action", two judicial sources say, the second alleged plot with links to Islamic State discovered in France this week.
Last Sunday, a car loaded with gas cylinders was found near Notre Dame cathedral and jerry cans of diesel, leading to the discovery of a plot to attack a Paris railway station under the direction of Islamic State.
Seven people, including four women, were arrested.
The boy had been under house arrest since France declared a state emergency after November 13 attacks in Paris in which Islamic State militants killed 130 people, two sources said on condition of anonymity. They did not say why he was under house arrest.
His arrest on Saturday came as he was planning an attack in a public place in the French capital, one of the sources said.
The second source said the boy had been in contact with suspected French Islamist militant Rashid Kassim and that Kassim also guided one of the women arrested last week in the plot to attack a train station in Paris.
French newspaper Le Monde reported that Kassim is in Syria. He has used Telegram, the messaging service, to call for more attacks in France.
"Women, sisters, go on, attack. Where are the brothers?...She brandished a knife and she hit a policeman... Where are the men?" Le Monde quoted a message of Kassim on Telegram.
One of the sources said Kassim, 29, inspired two men who carried out an attack in July in a French church during which they slit the throat of the elderly priest.
The attack shocked France, coming less than 12 days after another Islamic State militant drove a truck into crowds celebrating Bastille Day in Nice.