A total of 23 people have been arrested and dozens of weapons seized in a series of raids on suspected Islamist militants across France, officials say.
The crackdown follows multiple attacks on bars, restaurants, a concert hall and a stadium in Paris on Friday, in which 129 people were killed.
Belgian police say two people arrested on Saturday have been charged with "participating in a terrorist attack".
They were among seven people detained in Belgium at the weekend.
Five of them were later released, including Mohammed Abdeslam, the brother of two suspects - Brahim Abdeslam, killed during the attacks, and Salah Abdeslam, who is on the run.
France held a nationwide minute of silence at midday local time (11:00 GMT) for the victims.
President Francois Hollande led the minute's silence from the Sorbonne University - an acknowledgement of the young age of so many of the 129 who died, the BBC's Hugh Schofield reports from Paris.
The country has been slowly, awkwardly getting itself back into some form of routine, but because of the feelings triggered by Friday's horror, life still does not feel normal, our correspondent adds.
French PM Manuel Valls said the attacks had been organised from Syria.
He added that the authorities believed new terror attacks were being planned in France and other European countries.
Two more Paris attackers have been named, along with five already identified.
One is confirmed to have entered Greece as a migrant earlier this year, leading the head of the far-right Front National Marine Le Pen to demand that France immediately stop accepting new migrants "as a precaution".
She said that the government and opposition were "irresponsible" for agreeing to what she called "the flood of migrants".
As well as the attackers themselves, investigators are also reported to be focusing on a Belgian of Moroccan descent who is described as the possible mastermind of the attacks.
Abdelhamid Abaoud, 27, lived in the Molenbeek neighbourhood of Brussels, as did two of the attackers, and is now believed to be based in Syria, where he has risen through the ranks of IS.
Police have named Brussels-born Salah Abdeslam, 26, as a key suspect, and a manhunt is under way. He was reportedly stopped by officers in the wake of the attacks while crossing into Belgium but then let go.
Belgian police carried out a raid in the Molenbeek neighbourhood on Monday morning in an attempt to capture Salah Abdeslam, but no arrests were made.
Italian police have said they are searching in the Turin province for a 32-year-old French national named Baptiste Burgy, who is "suspected of being involved" in the attacks, the Ansa news agency reported.
Meanwhile, French aircraft have attacked Raqqa, the stronghold in Syria of the Islamic State group, which has said it carried out the attacks.
IS has issued a statement saying the raid targeted empty locations and that there were no casualties.
Mr Valls said France was dealing with a "terrorist army", rather than a single terrorist group.
"We know that operations were being prepared and are still being prepared, not only against France but other European countries too," he said.
Suspected Paris attackers
- Salah Abdeslam, 26 - urgently sought by police
- Brahim Abdeslam, 31 - named as attacker who died near Bataclan concert hall
- Omar Ismail Mostefai, 29, from near Paris - died in attack on Bataclan
- Bilal Hadfi, 20 - named as attacker who died at Stade de France
- Ahmad al-Mohammad, 25, from Idlib, Syria - died at Stade de France (unverified)
- Samy Amimour, 28, from near Paris - suicide bomber at Bataclan
- Two other attackers died during the assaults in the city
The prime minister said more than 150 raids on militant targets had been carried out in different areas of France early on Monday.
"We are making use of the legal framework of the state of emergency to question people who are part of the radical jihadist movement... and all those who advocate hate of the republic," he said.
Police sources told news agencies that properties in the Paris suburb of Bobigny, as well as the cities of Grenoble, Toulouse and Lyon, had been targeted.
Interior Minister Bernard Cazeneuve said 23 people had been arrested and dozens of weapons seized, including a Kalashnikov assault rifle and rocket launchers. More than 100 people have been placed under house arrest.
Seven attackers died in the assault on the French capital, most of them after detonating suicide belts.
Five were identified over the weekend. On Monday another two were named by the Paris prosecutor as Ahmad al-Mohammad and Samy Amimour.
- Al-Mohammad is the name on a Syrian passport found with the remains of one of the attackers, though the man's identity has not yet been verified. What has been confirmed is that his fingerprints match those taken by the Greek authorities after he arrived with migrants on the island of Leros in October 2015
- Amimour was said to be facing terrorism charges in France. He was placed under judicial supervision while under investigation for terrorist conspiracy - he planned to go to Yemen. An international arrest warrant was issued against him when he broke bail in autumn 2013. Three of his relatives were among those detained this morning
One of the main lines of investigation concerns Molenbeek, which has a reputation as being a haven for jihadists.
France is currently marking a second day of national mourning. A state of emergency declared by President Hollande remains in force. Thousands of extra police and troops are on the streets of Paris.
Main attack sites:
Bataclan concert venue, 50 Boulevard Voltaire, 11th district - 89 dead when stormed by gunmen, three of whom were killed; another gunman died nearby
La Belle Equipe, 92 rue de Charonne, 11th district - 19 dead in gun attacks
La Casa Nostra restaurant, 92 rue de la Fontaine au Roi, 11th district - five dead in gun attacks
Stade de France, St Denis, just north of Paris - three attackers and a bystander killed