At least 12 people have been killed in an attack on the Paris headquarters of the Charlie Hebdo satirical magazine, including Jewish caricaturist Georges Wolinski.

Video from the scene of today’s attack posted on the French news website shows two heavily armed men exiting a black car and shooting a rifle at a police officer near the building. One of the masked assailants then approaches the officer and shoots him in the head.

Ten people also were wounded in the attack; five are in serious condition.

The assailants had cried out “Allah is the greatest” in Arabic and that their attack was to “avenge the prophet,” the French daily Le Monde reported. They reportedly fled in a hijacked car, running over a pedestrian and shooting at officers.

“About a half an hour ago, two black-hooded men entered the building with Kalashnikovs,” a witness, Benoît Bringer, told the radio station France Info. “A few minutes later, we heard lots of shots.”

Charlie Hebdo, which regularly runs articles and caricatures critical of religion, has published a series of satirical cartoons of the Muslim prophet Mohammed.

The identities of the victims have not yet been made known.

Two of the reported fatalities were police officers, according to the French daily Le Monde. Employees of the satirical magazine also were reported killed.

“Time and again, the French people have stood up for the universal values that generations of our people have defended,” said US President Barack Obama today. “France, and the great city of Paris where this outrageous attack took place, offer the world a timeless example that will endure well beyond the hateful vision of these killers. We are in touch with French officials, and I have directed my administration to provide any assistance needed to help bring these terrorists to justice.”

The editorial teams of @VogueParis, @VanityFairFrance, @GQfrance, @glamourparis and @AD_magazine express sympathy and solidarity with the victims of this morning's attack on Charlie Hebdo, through Xavier Romatet, chairman of Condé Nast France. "Our colleagues at Charlie Hebdo were the victims of a terrible act of terrorism this morning, an unacceptable act of madness designed to attack freedom of expression and spread fear. The high price paid by the Charlie Hebdo team is a reminder that freedom of expression is an essential value. Now more than ever, we must defend it without compromise: this is the mission of journalism, across all sectors and across all media. My thoughts are, of course, with all those who paid for this liberty with their lives, and with their families. In the name of Condé Nast, I extend my deepest sympathies." Xavier Romatet Chairman of Condé Nast France #jesuischarlie

A photo posted by Vogue Paris (@vogueparis) on

Wolinski, 81, a French Jew who was born in Tunisia and moved to France at 13, has worked at leading publications such as L’Humanite, Le Nouvel Observateur and Paris Match.

French President Francois Hollande, speaking live near the scene of the shooting, said it was a terrorist attack, adding that “France is today in shock.”

Charlie Hebdo, he added, “was threatened several times in the past and we need to show we are a united country.” He also vowed that French authorities “will punish the attackers. We will look for the people responsible.”

The French cabinet is expected to meet in an emergency session at 2 p.m., according to officials.

In a statement, European Jewish Congress President Moshe Kantor called the attack part of “the beginning of a wave of terror on the streets of Europe” and “a war against freedom of speech and the European way of life which has already seen Jewish children gunned down at school and people murdered in cold blood while visiting a museum in Brussels.”

Sammy Ghozlan, president of the National Bureau for Vigilance Against Anti-Semitism, said in a statement that “France must wake up to the danger of Islamism and the terror it brings all over the world: In Paris, Toulouse, Sarcelles, Brussels, Jerusalem and Tel Aviv, jihadists are acting on the same radical Islamist ideology that is used to manipulate them.”

Israeli Foreign Minister Avigdor Lieberman sent his condolences to the French people and said that Israel sympathizes with France’s pain after the attack, The Jerusalem Post reported.

According to Le Monde, the attack on the Charlie Hebdo offices is the bloodiest to have taken place in France since 1835.