PARIS
— President François Hollande of France called on Monday for
constitutional amendments to fight potential terrorists at home and for
an aggressive effort to “eradicate” the Islamic State abroad.
His
call to arms — “France is at war,” he said at the opening of his
remarks to a joint session of Parliament — came as security forces in
France and Belgium zeroed in on a suspect they said was the architect of
the assault that killed 129 people Friday night in Paris. The suspect, a
27-year-old Belgian, has fought for the Islamic State in Syria and has
been linked to other terrorist attacks.
Mr.
Hollande spoke after the French police raided homes and other sites
across the country in an effort to head off possible further attacks and
as the authorities in Belgium hunted for a suspected assailant in
Friday’s attacks. Mr. Hollande called for quick action by Parliament on new legislation
that would give the government more flexibility to conduct police raids
without a warrant and place people under house arrest. He said he would
seek court advice on broader surveillance powers. And he called for
amendments that would enable the state to take exceptional security
measures without having to resort to the most drastic options currently
in the Constitution.

Mr.
Hollande is also seeking to extend the current state of emergency for
three months and let the government strip the citizenship of French
natives who are convicted of terrorism and hold a second passport.
“Our
democracy has prevailed over much more formidable opponents than these
cowardly assassins,” Mr. Hollande said a day after France conducted
airstrikes against the Syrian city of Raqqa, the self-proclaimed capital
of the Islamic State. It was the country’s most intense military strike
yet against the radical group, which has claimed responsibility for the
attacks in Paris.
The
French leader said he would meet soon with President Obama and
President Vladimir V. Putin of Russia in an effort to settle on a united
campaign to wipe out the Islamic State, also known as ISIS or ISIL.
“Terrorism will not destroy the republic, because it is the republic that will destroy it,” he said.
Three
days after the attacks on a soccer stadium, a concert hall and numerous
bars and cafes, French and Belgian security services were focused on
the radical jihadist they believe was the leader of the plot, Abdelhamid Abaaoud. He is among the most prominent Islamic State fighters to have come out of Belgium.
A
French official briefed on the investigation, who spoke on the
condition of anonymity because he was not authorized to discuss
operational details, said Mr. Abaaoud had mentioned plans to attack “a
concert hall” to a French citizen who returned from Syria.
Mr.
Abaaoud, this official said, had also been in contact with Ismaël Omar
Mostefaï, one of the Paris attackers. Mr. Abaaoud also knew another
attacker, Ibrahim Abdeslam; they were tried together in 2010 in Belgium
for a minor offense.
Mr. Hollande said the attacks had been “planned in Syria, organized in Belgium, perpetrated on our soil with French complicity.”
The
French authorities said Monday that they had conducted 168 raids across
the country in an effort to root out possible terrorist threats. The
raids extended from the Paris region to the major cities of Lille, Lyon,
Marseille and Toulouse, they said. They also said they had arrested 23
people and detained 104 others under house arrest.
But
a Frenchman believed to be involved in the Paris attacks, Salah
Abdeslam, 26, a brother of Ibrahim Abdeslam, remained at large, eluding a
series of raids conducted by the authorities in Molenbeek, the
working-class Brussels neighborhood where the brothers lived.
A
third brother, Mohamed, and four other men who had been detained in
Belgium were released on Monday. At a news conference in Brussels,
Mohamed said he did not know Salah’s whereabouts and added, “My parents
are under shock and have not yet grasped what has happened.”as the Abdeslam brothers.
Mr.
Abaaoud was already a suspect, according to officials and local news
reports, in a failed terrorist plot in Belgium in January and an attempt
in August to gun down passengers on a high-speed train to Paris from Brussels. An intelligence official said the authorities feared he might be in Europe.
In
Washington, Representative Adam B. Schiff of California, the senior
Democrat on the House Intelligence Committee, said some American
officials suspected that Mr. Abaaoud might still be in Syria. Mr.
Abaaoud was most likely part of an Islamic State cell that has developed
over the past year to help plan, organize and execute terrorist attacks
in Europe, particularly in France, Mr. Schiff said in a telephone
interview.
The
cell is believed to be led by Abu Mohammed al-Adnani, who serves as an
official spokesman for the Islamic State, a Defense Department official
said Monday.
Mr.
Schiff warned that much was still unknown about how much of the plot
had been directed from Syria and how much autonomy had been left to
conspirators.cities — Delhi; Doha, Qatar; and Dublin — crowds gathered at French embassies to pay their respects.
As
France observed its second of three days of national mourning, the
authorities in France and Belgium raced to track down suspects and chase
leads.
At
one house in the Rhône department in the southeast, around Lyon, the
police found a Kalashnikov rifle, three pistols, ammunition and
bulletproof vests. Officers then obtained a warrant to search the home
of the parents of a man who lived in the house, where they found several
automatic pistols, ammunition, police armbands, military clothing and a
rocket launcher.
Prime
Minister Manuel Valls and Interior Minister Bernard Cazeneuve promised
to keep up the search. “We are using all the possibilities given to us
by the state of emergency, that is to say administrative raids, 24 hours
a day,” Mr. Valls said. He vowed to keep intense pressure on “radical
Islamism, Salafist groups, all those who preach hatred of the Republic.”