Updated

French police have arrested a 16-year-old at his Paris home to abort what they feared was a planned weekend attack, as the prime minister warned some 15,000 people in the country could be in the process of being radicalised.

A security official said that France's intelligence services "detected a threat" and a judicial official said police moved into action on Saturday fearing a planned attack this weekend.

Both officials said the arrest was not linked to the arrests last week of four women, a 15-year-old daughter of one of the women and a man over aborted attacks, including one near Notre Dame Cathedral.

Intelligence agents suspected the boy planned to carry out a knife attack in a public place this weekend, the judicial official said, refusing to name a spot where it was thought the attack might occur.

France is in a state of emergency after three attacks this year, including the Bastille Day truck attack in Nice that killed 86 people. That followed two waves of attacks last year, notably the November 13 attacks on restaurants, bars, a concert hall and stadium that left 130 people dead.

News of the arrest followed shortly after Prime Minister Manuel Valls said on Sunday that "every day attacks are foiled... (including) as we speak."

Mr Valls said nearly 15,000 people in France are being tracked because they are suspected of being in the process of radicalisation, while 1,350 are under investigation for having links to terrorism.

"Today the threat is at a maximum, and we are a target," Mr Valls said on Europe 1 radio. "Every day intelligence services, police foil attacks, dismantle networks, track terrorists."

Mr Valls added that despite the plots uncovered, "There will be new attacks. There will be innocent victims."

The teenage boy had been placed under house arrest this summer due to France's state of emergency, after a search of his home, the judicial official said.

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