Masked gunmen opened fire in the offices of a French satirical newspaper on Wednesday in Paris, the police said, with initial reports saying that as many as 12 people had been killed and 10 wounded.

Xavier Castaing, the head of communications for the Paris police headquarters, said that 11 people had died, The Associated Press reported. However, a senior French prosecutor raised the toll to 12 in the early afternoon.

The news channel France Info quoted a witness as saying that he saw the episode from a nearby building in the heart of the French capital.

“About a half an hour ago, two black-hooded men entered the building with Kalashnikovs,” the witness, Benoît Bringer, told the station.

“A few minutes later, we heard lots of shots,” he said, adding that the men were then seen fleeing the building.

President François Hollande was headed to the scene of the shooting, in the 11th Arrondissement. He said the shooting was “undoubtedly a terrorist attack” and ordered the nation’s terror alert status raised to the highest level.

He also said that several terrorists attacks had been thwarted in recent weeks. The French authorities added security at houses of worship, news media offices and transportation hubs.

The cabinet was set to meet in an emergency session at 2 p.m., officials said.

The newspaper, Charlie Hebdo, has been attacked in the past for satirizing Islam and the Prophet Muhammad. Its offices were firebombed in 2011 after publishing a cartoon of the prophet on its cover promising “100 lashes if you don’t die laughing!”