In front of the city hall of Rennes, people honor the victims of the attack by raising pens into the air. Damian Meyer / AFP / Getty Images

A gathering at the Place Royale in Nantes to show their solidarity for the victims of the attack by unknown gunmen on the offices of the satirical weekly, Charlie Hebdo. Georges Gobet / AFP / Getty Images

Journalists hold placard reading "I am Charlie" as they hold a minute of silence, on January 7, 2015 at the redaction of French news agency Agence France Presse, following the attack by gunmen in the offices of the French satirical weekly Charlie Hebdo. Bertrand Guay/Getty Images

Flowers and a note saying 'Je suis Charlie' are placed in front of the French Embassy in the German capital Berlin, following a shooting at the French satirical magazine 'Charlie Hebdo' in Paris. Bernd von Jutrczenka/EPA

People like candles during a rally in support of the victims of the attack by gunmen at French satyrical newspaper Charlie Hebdo at the Place de la Republique in Paris, on January 7, 2015. Martin Bureau/AFP/Getty Images

People gather for a rally in solidarity with the killed Charlie Hebdo employees, in Geneva, Switzerland, after two masked gunmen with automatic rifles killed 12 people at the Paris headquarters of satirical French magazine Charlie Hebdo.

People hold up placards reading in French, "I am Charlie" during a gathering in Nice, southeastern France, on January 7, 2015, following an attack by unknown gunmen on the offices of the satirical weekly, Charlie Hebdo. Valery Hache/AFP/Getty Images

People gather for a rally in solidarity with the killed Charlie Hebdo employees, in Geneva, Switzerland. Martial Trezzini/EPA

Tens of thousands of people joined rallies in Paris and other French cities Wednesday to pay tribute to the victims of an attack by gunmen at the satirical weekly newspaper Charlie Hebdo.

In Paris, crowds of people swarmed into the Place de la Republique, which lies barely a half a mile from the scene of the killings that have stunned France.

At least 20,000 people also gathered in the French cities of Lyon and Toulouse, police said, after the heavily armed attackers killed12 people.

Demonstrators wore black stickers reading "Je suis Charlie" (I am Charlie), a slogan aimed at showing solidarity with the victims of the deadliest such attack in France in decades.

Others waved banners with slogans such as "Press freedom has no price" and "Charb mort libre" (Charb died free), a reference to the newspaper's slain editor-in-chief Stephane Charbonnier.

Charbonnier was one of four cartoonists killed in the attack that also left 11 people injured.

"It's terrible that these people were murdered. In future, no one will be able to speak his mind. We have to demonstrate in our thousands," said Beatrice Cano, a protester in her fifties, who was carrying the latest issue of Charlie Hebdo.

Other cities around the world were also planning rallies to pay tribute to the dead.

Agence France-Presse