The suspected ringleader of the Paris attacks, Abdelhamid Abaaoud, was among those killed in a French police raid yesterday, prosecutors say.
They confirmed the Islamic State (IS) militant had died in a flat in the Paris suburb of Saint Denis.
His body was found riddled with bullets and shrapnel in the apartment.
Interior Minister Bernard Cazeneuve said he had received intelligence that Abaaoud had passed through Greece on his return from Syria.
It is unclear whether the Belgian had concealed himself among the thousands of migrants arriving in Greece before heading for other EU nations.
Friday’s gun and suicide bomb attacks in the French capital left 129 people dead and hundreds injured.
One of the other attackers, who blew himself up outside the Stade de France, was traced to Greece by his fingerprints, where he was registered as a migrant.
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Confirming Abaaoud left for Syria last year, Mr Cazeneuve said no EU states had signalled his return.
The minister also implicated Abaaoud in four out of six attacks foiled in France since this spring.
He was linked to a plot in April to attack a church near Paris. Police are also investigating a possible connection to the attack on a high-speed train from Amsterdam to Paris in August.
In Belgium, he had links to an Islamist cell that was broken up in a raid by security forces in the town of Verviers in January which led to the deaths of two gunmen.
Police sources told AFP news agency that the tip-off about Abaaoud’s presence in Greece had come from Moroccan intelligence.
Eight people were arrested and at least two killed in the raid on the property in Saint Denis. Heavily armed police stormed the building after a tip-off that Abaaoud was in Paris.
A woman at the flat – reported in French media to be Abaaoud’s cousin – died during the raid after activating a suicide vest.
The prosecutor’s office said it was still unclear whether Abaaoud had blown himself up or not. The 28-year-old was identified from his fingerprints.
Mr Cazeneuve told reporters that a non-EU state had alerted France on Monday that Abaaoud had been in Greece.
“Everyone must understand it is urgent that Europe wakes up, organises itself and defends itself against the terrorist threat,” he said.
The BBC’s Hugh Schofield in Paris says the identification of Abaaoud raises serious questions for security services.
He was high on French and Belgian wanted lists and yet managed to travel from Syria to the heart of Paris without ever leaving a trace.
Investigators are still looking for another suspect, Salah Abdeslam, who is believed to have travelled to Belgium after the attacks on Friday night.