French authorities launched a massive dragnet this week following the massacre at the satirical newspaper Charlie Hebdo. Here are the key moments so far. (Jorge Ribas/The Washington Post)

Prime Minister Manuel Valls declared Saturday that France was at “war” with radical Islam after three days of bloody attacks around Paris that sparked fears of a tide of violence by militants living in Europe.

French leaders called for their nation to turn out Sunday in support of victims of the brazen attacks that paralyzed the country. Authorities said they would deploy thousands of police officers and soldiers to secure the nationwide rallies, in a marker of the newfound sense of vulnerability and fear that has struck this diverse country proud of its history of tolerance. French President François Hollande convened his top security advisers Saturday, a sign of the deep-seated worry about further violence.

Authorities were still searching for Hayat Boumeddiene, 26, the partner of the man who is alleged to have killed a police officer Thursday and four more people at a kosher grocery store Friday. Those actions occurred just after a rampage allegedly carried out by his associates at the offices of a satirical newsweekly that had published cartoons mocking Islam.

By Saturday evening, French security officials said they believed that Boumeddiene had fled to Turkey on Jan. 2 and that she may have gone to Syria on Jan. 8, the same day her partner killed the police officer.

The Syrian connection raised further questions about the assailants’ ties to Islamist militant groups. Boumeddiene’s partner, Amedy Coulibaly, said Friday that he had organized his attacks in conjunction with the Islamic State, a brutal insurgent organization that controls large portions of Syria and Iraq. Thousands of native-born European citizens are believed to have slipped into Syria to fight in a civil war that has become ground zero for global Islamist militancy.

France is in a “war against terrorism, against jihadism, against radical Islamism, against everything that is intended to break fraternity, liberty, solidarity,” Valls told an audience in Evry, a town south of Paris.

The three days of attacks were the most lethal terrorist assault in France since Algerian insurgents bombed a string of locations in this country during the former French colony’s fight for independence in the 1950s. Law enforcement officials pledged Saturday to hunt down Boumeddiene, a French native whom they believe had trained alongside her partner.

“We will do everything in our power to find her,” said Christophe Crepin, a senior police official. He vowed that she would not escape French law enforcement even if she were in Syria. “We are at war, and we will take the necessary measures,” he said.

Many French leaders emphasized the scale of the fight ahead of them, even as profound questions were raised about the future of France’s status as a tolerant, multicultural nation. Muslims have long had a vibrant presence here, a legacy of France’s colonial involvement in Africa and the Middle East, but a far-right, anti-immigrant party was topping some polls even before the attacks.

Valls and other French leaders have discouraged the far-right National Front party from taking part in Sunday’s rallies. But the party’s leader, Marine Le Pen, hit back forcefully Saturday, saying, “We will not submit to the brutality of those who exclude us from the nation.” She called on her supporters to stay away from the demonstration in Paris but to participate in gatherings elsewhere.

Critics have said the National Front is a racist organization that has done little to repudiate past anti-Islamic and anti-Semitic views.

World leaders to attend rally

It was unclear what role Boumeddiene played in the attacks that started Wednesday, when brothers Chérif and Said Kouachi are alleged to have opened fire at the offices of the Charlie Hebdo newsweekly, killing 12. Boumeddiene’s partner, Coulibaly, who was radicalized in the same prison in 2005 as Cherif Kouachi, allegedly began his own killing spree by shooting the police officer the next day.

Two hostage situations related to Wednesday's massacre at the satirical newspaper Charlie Hebdo ended Friday evening Paris time when police simultaneously stormed both sites. All three suspects were killed.

French security forces killed all three men Friday in the bloody denouement to what had become a double hostage crisis. A top prosecutor said Friday that Boumeddiene and the wife of one of the brothers had called each other more than 500 times in 2014. The brothers said they had been supported by Anwar al-Awlaki, an American-born cleric who was slain while serving as a leader of al-Qaeda in the Arabian Peninsula, a rival of the Islamic State.

A fuller portrait of Boumeddiene emerged Saturday, as accounts described her evolution from a woman who donned bikinis to a fighter who quit a job as a cashier rather than abandon the full-face veil, which is illegal in France. One of seven children, she was only 6 years old when her mother died, and as her father struggled to support the family, she entered the custody of French social services when she was 8 or 9, according to a profile in the daily Parisien newspaper. In 2010, she refused to condemn al-Qaeda when being interrogated by anti-terrorism investigators and instead complained of the “innocents killed by Americans,” the weekly Nouvel Observateur reported, citing investigation documents.

On Saturday, French Interior Minister Bernard Cazeneuve said the country remained on the highest security alert. The leaders of Britain, Germany, Italy, Spain, Israel and other countries planned to attend the Sunday rally in Paris. The United States was sending Attorney General Eric H. Holder Jr., who also planned to take part in a meeting of top law-enforcement officials from around the world. Turkish Prime Minister Ahmet Davutoglu also said he would attend, making him the highest-profile official from the Muslim world.

French authorities have said that Coulibaly and one of the brothers involved in the attack on Charlie Hebdo belonged to the same militant network, named for the Buttes Chaumont park in Paris where they exercised. Coulibaly and the brother, Chérif Kouachi, were reportedly radicalized when they met Djamel Beghal, a French Algerian jihadist convicted of plotting to attack the U.S. Embassy in Paris in 2001.

All three men were known to French authorities, and Coulibaly was imprisoned as recently as 2013 over an attempt to free another Islamist militant from prison. But he was later freed and apparently unmonitored.

Police on Saturday released the five remaining people they had detained in connection with the attacks, Agence France-Presse reported. A day earlier, they freed Hamyd Mourad, the 18-year-old brother-in-law of Chérif Kouachi, who was initially suspected of participation in the Wednesday violence but was subsequently cleared.

Many residents of Paris said they were struggling to contain both anger and fear about the specter of homegrown insurgency.

“France has a history of resistance, and we need to resist now. Not through violence, but perhaps another way,” said Lucie Cabourdin, 34, a television producer who visited her local police station Saturday to leave a yellow rose for a slain officer. “I just want to walk the streets naked with a sign that says, ‘Oops, I forgot my burqa this morning.’ I know it’s ridiculous, but it would be symbolic. This is France, and I will do whatever I want to do.”

Griff Witte contributed to this report.