French prosecutors confirmed Belgian citizen Abdelhamid Abaaoud had died in a flat in the Paris suburb of Saint-Denis.
Abdelhamid Abaaoud’s body was found riddled with bullets and shrapnel in the apartment.
Interior Minister Bernard Cazeneuve said he had received intelligence that Abdelhamid Abaaoud passed through Greece on his return from Syria.
It is unclear whether Abdelhamid Abaaoud had concealed himself among the thousands of refugees arriving in Greece before heading for other EU nations.
One of the other dead Paris attackers, who blew himself up at the Stade de France stadium, was traced to Greece by his fingerprints, where he was registered as a refugee.
In another development, nine arrests were made in Belgium after searches in connection with Paris attacks, and police carried out new searches in France.
Confirming Abdelhamid Abaaoud left for Syria last year, Bernard Cazeneuve said no EU states had signaled his return.
The minister also implicated Abdelhamid Abaaoud in four out of six attacks foiled in France since this spring.
Abdelhamid Abaaoud, 28, was linked to a plot in April to attack a church near Paris and police are also investigating a possible connection to the attack on a high-speed train from Amsterdam to Paris in August.
In Belgium, Abdelhamid Abaaoud had links to an Islamist cell broken up by security forces in the town of Verviers in January, with the deaths of two gunmen.
He was identified from his fingerprints.
Paris attacks left 129 people dead and hundreds injured.
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 Abdelhamid Abaaoud was in Paris.
A woman at the flat – reported in French media to be Abdelhamid Abaaoud’s cousin – died during the raid after activating a suicide vest.
The prosecutor’s office said it was still unclear whether Abdelhamid Abaaoud had blown himself up or not.
Bernard Cazeneuve told reporters that a non-EU state had alerted France on November 9 that Abdelhamid Abaaoud had been in Greece.
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