French Interior Minister Bernard Cazeneuve has said European countries must "wake up" to terror threats, following the attacks in Paris that left 129 people dead.
He spoke after it emerged that the suspected Belgian ringleader of the attacks had entered France undetected.
Belgian PM Charles Michel has defended Belgium's security services amid claims the attacks were organised there.
It comes as EU interior ministers are due to hold emergency talks.
The meeting in Brussels is expected to tighten checks at the external borders of the EU's passport-free Schengen area.
Key questions remain after attacks
On Thursday, French prosecutors confirmed that Islamic State (IS) militant Abdelhamid Abaaoud was among those killed in a police raid the previous day.
His bullet-riddled body was found in the wreckage of a flat in the Paris suburb of Saint-Denis.
Investigators had identified him as the most likely organiser of last Friday's attacks, but it was initially thought he was in Syria.
At a news conference, Mr Cazeneuve said "no information" had been received from other European countries about his arrival on the continent.
But he said he had received intelligence that Abaaoud had passed through Greece on his return from Syria.
"It is urgent that Europe wakes up, organises itself and defends itself against the terrorist threat," Mr Cazeneuve told reporters.
French Prime Minister Manuel Valls said some of those involved in the attacks had taken advantage of the migration crisis in Europe - which has seen thousands of asylum seekers arrive on the continent - to "slip into" France unnoticed.
One of the attackers, who blew himself up outside the Stade de France, has been traced by his fingerprints to Greece where he was registered as a migrant.
Abaaoud's movements
2013: Said to have first visited Syria, joining the Islamic State group before slipping back to his home country, Belgium
20 January 2014: Passes through Germany's Cologne-Bonn airport, en route to the Turkish city of Istanbul. Returns to Syria, where he becomes one of the faces of IS propaganda
15 January 2015: His mobile phone is reportedly traced to Greece from calls made to an Islamist cell in Verviers, Belgium
16 November 2015: Three days after the Paris attacks, a foreign intelligence service alerts France that he is back in Europe, having passed through Greece; police receive a tip-off that he is on French territory
18 November 2015: Killed in police raid on Paris suburb of Saint-Denis, five days after reportedly heading the attacks in Paris that left 129 people dead
