The attackers at the Bataclan concert hall evoked Syria and Iraq during their killing spree in Paris, according to Paris Prosecutor Francois Molins.
In a press conference, he said three teams seem to have coordinated the attacks that left 129 people dead another 352 injured across the French capital. 99 remain in a critical condition and the number of dead is expected to rise.
Meanwhile, French authorities have placed the father and brother of one of the Bataclan Concert Hall attackers in custody.
Molins earlier said the French authorities had a security file on one of the Bataclan attackers.
Born on 21 November 1985, and from the Parisian suburb of Courcouronnes, he has been known to police since 2004 and was flagged as an extremist in 2010.
Another gunman was found near a Syrian passport. He was born in 1980 and had not been known to French police.
A Greek minister has said that the Syrian passport found at the scene of the deadly attack at Stade de France stadium belonged to someone who had got into the EU via Greece.
He passed through the island of Leros in October, though Citizen Protection Minister Nikos Toskas says he doesn't know whether other countries also checked the man's ID.
Greek government sources later added that is is “very likely” that a second gunman entered the EU through Greece, Reuters reports.
French broadcaster BFMTV also said an Egyptian passport was found close to the body of one of the assailants.
Three of the eight suspects lived in Brussels, according to reports in Belgian media.
"A number of" people have been arrested after raids were carried out in the Molenbeek area of the city, the country's Justice Minister has confirmed.
The Belgian prosecutor's office has opened an anti-terrorist investigation linked to the terror in Paris and will examine a car that had been hired in Belgium and was found near the Bataclan concert hall.
It comes after French media said officers wanted to trace a suspicious black car with Belgian plates that was seen near the Bataclan venue, where more than 80 people were killed.
Meanwhile, a police source in France has said one of the bombers was a young French man known for links with Islamic extremism.
The same source said that the gunman had been identified by his fingerprints.
Islamic State has claimed responsibility for the multiple attacks across the capital - and has warned that France would remain at the "top of the list of targets" over its airstrikes on IS territory in Syria and Iraq.
It said in an online statement that eight militants armed with explosive belts and guns chose targets "in the capital of adultery and vice".
In Germany, officials have said a 51-year-old man arrested with weapons in his car last week may be linked to the Paris attacks.
Firearms, explosives and hand grenades were found in the vehicle near the German-Austrian border - but Bavarian state police would not confirm reports that the man appeared to be en route to Paris when he was held.
