The suspected mastermind of the Paris attacks has been identified, as authorities mounted a massive security operation amid growing questions about how the terrorists evaded detection.
Belgian Abdelhamid Abaaoud has been singled out as a key figure in the plot that saw 129 people murdered in coordinated strikes in the French capital on Friday.
He is believed to be linked to thwarted attacks on a Paris-bound high-speed train and a church in the Paris area, an official said.
It came as Interior Minister Bernard Cazeneuve revealed that 168 locations across France were raided overnight, with 104 people placed under house arrest in the past 48 hours.
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 war-ravaged country.
His fingerprints matched those of someone who passed through Greece in October.
In another development, 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.
A huge security operation continues in the Brussels suburb of Molenbeek as police hunt for Salah Abdeslam, 26, who rented a car used to carry gunmen to the Bataclan.
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.
David Cameron confirmed that UK intelligence and security agencies had thwarted seven smaller-scale attacks over recent months - one more than had previously been known about.
Speaking at a press conference on the second day of the G20 summit, the Prime Minister said that leaders had agreed "important steps" to counter the threat from terrorism.
These included measures to cut off financing for terror groups, counter extremist ideologies and propaganda and improve security at airports.
He has also announced plans to recruit 1,900 security and intelligence agents and double spending on aviation security in response to the terror threat from Islamic State.