*United Nations also condemn attack

Tens of thousands of people joined rallies in Paris and other French cities on Wednesday to pay tribute to the victims of a massacre by Islamist gunmen at the satirical weekly Charlie Hebdo.

In Paris, crowds of people swarmed into the Place de la Republique that lies barely a kilometre (half a mile) from the scene of the bloodbath that has shocked France.

At least 20,000 people also gathered in the French cities of Lyon and Toulouse, police said, after 12 people were killed by heavily armed gunmen screaming “Allahu akbar” (God is greatest).

Demonstrators wore black stickers marked “Je suis Charlie” (I am Charlie), a slogan aimed at showing solidarity with the victims of the deadliest 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 demonstrator 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.

The UN Security Council on Wednesday strongly condemned the “barbaric and cowardly terrorist attack” in Paris against the French weekly Charlie Hebdo that killed 12 people.

“The members of the Security Council strongly condemned this intolerable terrorist act targeting journalists and a newspaper,” said a statement from the 15-member council.

The council stressed the need to bring the perpetrators to justice and reaffirmed that “acts of terrorism are criminal and unjustifiable”.

Twelve people including the weekly’s chief editor and three cartoonists were killed when gunmen burst into the publication’s Paris offices and opened fire, shouting “Allahu Akbar” (God is greatest).

The attack took place at a time of heightened fears in France and other capitals over fallout from the wars in Iraq and Syria, where thousands of foreign citizens have joined the ranks of the radical Islamic State group.

Secretary General Ban Ki-moon earlier voiced outrage over the attack and branded it an assault on the media and freedom of expression.

“It was a horrendous, unjustifiable and cold-blooded crime. It was also a direct assault on a cornerstone of democracy, on the media and on freedom of expression,” Ban told reporters at UN headquarters.

“This horrific attack is meant to divide. We must not fall into that trap,” he added.

“This is a moment for solidarity around the world. We must stand strong for freedom of expression and tolerance and stand against the forces of division and hate.”