About 700,000 people are said to have taken part in marches across France following three days of deadly attacks in the Paris area.
They were held in cities including Paris, Orleans, Nice, Pau, Toulouse and Nantes, to commemorate the victims of this week’s violence.
Seventeen people were killed in attacks on a satirical magazine, police officers and a kosher supermarket.
Police are hunting for accomplices of the three gunmen, killed by police.
The interior minister says France will stay on high alert in the coming weeks.
During the marches, held largely in silence, some protesters held banners that read “I am against racism”, “unity”, or “I am Charlie” – the latter a reference to Charlie Hebdo, the satirical magazine whose Paris offices were attacked by brothers Cherif and Said Kouachi on Wednesday.
Twelve people – including eight journalists and two police officers – were killed and 11 injured in that attack. Another gunman, Amedy Coulibaly, took several hostages at a kosher supermarket in eastern Paris on Friday. Four hostages were later found dead.
Coulibaly is also believed to be behind the killing of a policewoman in southern Paris on Thursday.
Addressing a large gathering outside the kosher supermarket that was targeted, Prime Minister Manuel Valls said: “Today, we are all Charlie, we are all police officers, we are all Jews of France.”
There was tight security in Paris on Saturday, where some 500 extra troops are being deployed to back up the existing police and army presence.
The family of Ahmed Merabet, one of the police officers killed during Wednesday’s attack, gave an emotional news conference on Saturday.
Mr Merabet was “Muslim, and very proud of being a police officer and defending the values of the Republic”, his brother Malek Merabet said.
“Our family is devastated by this act of barbarity, and shares the pain of the families of all the victims.”
Malek Merabet added that “racists, Islamophobes and anti-Semites” should not confuse extremists with Muslims.
The family said they were “proud” of the gatherings that had taken place to commemorate the victims, saying they proved that France could be united.
Supermarket victims named
The violence began on Wednesday when Cherif and Said Kouachi, both heavily armed, attacked the offices of Charlie Hebdo magazine.
The brothers then went on the run, before becoming surrounded by police at a printworks warehouse in Dammartin-en-Goele, 35km (22 miles) north of Paris, on Friday. They were eventually killed after exchanging fire with police.
One hostage at the warehouse had been released earlier and a second employee, who was hiding in the building’s cafeteria, was freed by police.
Also on Friday, Amedy Coulibaly took several hostages at a kosher supermarket in eastern Paris.
He had threatened to kill the hostages unless the Kouachi brothers were released.
Police stormed the supermarket on Friday evening, killing Coulibaly and rescuing 15 hostages. They found the bodies of four hostages who are believed to have been killed before the assault.
The four victims have been named as Yoav Hattab, Philippe Braham, Yohan Cohen, and Francois-Michel Saada. Their names were released by the Representative Council of French Jewish Institutions.
Police are searching for Hayat Boumeddiene, Coulibaly’s partner.
Police sources and Turkish officials have said she may have been out of the country at the time of the attacks. They believe she left France for Turkey, possibly en route to Syria.
Police had previously identified her as a suspect in Thursday’s shooting of a policewoman.
Said Kouachi was known to have travelled to Yemen in 2011, while he and his brother are understood to have been on UK and US watch-lists.
According to French prosecutors, Coulibaly knew one of the brothers and their respective partners had spoken on the phone more than 500 times.
Interior Minister Bernard Cazeneuve said all necessary measures were being taken to protect the country.
He also promised “exceptional measures” for a massive unity march in Paris on Sunday, including snipers on roofs and a total of more than 5,500 police and military personnel.
Those set to attend Sunday’s rally include UK Prime Minister David Cameron, German Chancellor Angela Merkel, Turkish Prime Minister Ahmet Davutoglu, Spanish Prime Minister Mariano Rajoy and Russian Foreign Minister Sergei Lavrov.
The rally will depart from Paris’s Place de la Republique at 15:00 local time (14:00 GMT).
Families of the victims have begun to speak out about the attacks.