French security officials have honed in on a Belgian-born IS fighter as the likely mastermind of the Paris attacks that killed 129 and wounded more than 300
Abdelhamid Abaaoud, who is of Morroccan descent, is also believed to be linked to thwarted attacks on a Paris-bound high-speed train and a church in the Paris area.
RTL radio in France reported that the 27-year-old is "one of the most active Isis executioners" in Syria.
Abaaoud allegedly oversaw the attack and funded it. He was suspected of planning a series of foiled terror attacks and his phone was traced to Greece.
Said to be the son of a shopkeeper from Morocco, Abaaoud reportedly joined Isis in Syria in 2013 and appeared in a video driving a van carrying a pile of mutilated bodies to a mass grave.
Belgian media reported that he recruited his own 13-year-old brother, Younes Abaaoud, who is believed to be one of the youngest fighters in the so-called Islamic State.
Abaaoud, who goes under the name Abu Umar al-Baljiki, is thought to have taken part in various IS battles and executions.
Abaaoud is believed to have carried out several armed robberies with two brothers who are implicated in the Paris attacks. It has also been reported that "a French jihadi arrested after returning from Syria this summer reportedly told police Abaaoud had told him to attack a concert hall.
France's Interior Minister Bernard Cazeneuve yesterday revealed that 168 locations across the country were raided, with 104 people placed under house arrest on Sunday and yesterday. Several more individuals have been detained, while officers have seized dozens of weapons including a Kalashnikov assault rifle and automatic pistols.
"This is just the beginning. These actions will continue.The reply of the republic will be solid and total. Those who want to hurt the republic, they will be attacked, they will be dealt with, and who helped them," Mr Cazeneuve said.
As a minute's silence was observed in tribute to the victims of the massacre, further details about the culprits emerged, triggering fresh scrutiny of possible intelligence failures.
It was revealed that one of the suicide bombers who blew himself up in the Bataclan music hall had featured in a previous terrorism investigation, but slipped through the net.
Officials identified the assailant as Samy Amimour, a 28-year-old Frenchman, who had been charged in a terror probe in 2012.
He was placed under judicial supervision but dropped off the radar - prompting authorities to issue an international arrest warrant.
An attacker who blew himself up outside the national soccer stadium was found with a Syrian passport in the name of Ahmad Al Mohammad, a 25-year-old born in Idlib, a city in the north-west of the country.
His fingerprints matched those of someone who passed through Greece in October.
Claims emerged that Turkish authorities flagged one of the attackers to their French counterparts last year, but received no response until after Friday's assault.
An official was reported to have said that Omar Ismail Mostefai was identified as a possible "terror suspect" in October 2014, with French authorities said to have been alerted in December 2014 and in June 2015.
French authorities missed an opportunity to detain him when he was questioned and released just hours after the carnage in Paris. Abdeslam is one of three brothers linked to the atrocity.
Meanwhile, British intelligence services have foiled seven terror attacks in the past year, including one in the last month, Prime Minister David Cameron has said.
Mr Cameron warned that while the plots were on a smaller scale than what has been witnessed in Paris, the attacks in the French capital were "the sort of thing we have been preparing for".
Mr Cameron told a press conference at the G20: "Obviously I can't go into too much detail. It is seven plots that have been started in the previous months."
IS has released a new propaganda video praising the Paris attacks and threatening to launch an attack on the US capital, and other countries involved in the international coalition bombing its strongholds.
Dozens of Belgian police and armed commandos surrounded houses yesterday in the Brussels district of Molenbeek, which is home to many Muslim immigrants. Police arrested seven suspects in Brussels over the weekend, five of whom have been released, and are hunting Salah Abdeslam (26), a Frenchman based in the Belgian capital, who is one of three brothers believed to have been involved in the plot.