Four cartoonists reported to be among 12 killed in gun attack on French magazine which ran Islamic caricatures

French newspaper Le Monde reported that cartoonist Georges Wolinski had also been killed.

A massive manhunt has now been launched for three fugitive gunmen who carried out the deadly terror attack.

The massacre this morning was France's deadliest terror attack in at least two decades and prompted outrage and condemnation from political leaders including First Minister Nicola Sturgeon.

In a statement tonight, Ms Sturgeon said: "This is a horrific and appalling crime, and my heart goes out to all of those affected by today's dreadful events.

"My thoughts are with the people of France, with whom we in Scotland share so many close ties. Today's attack once again demonstrates the need for all democracies to stand firm in the face of terrorist atrocities."

The Queen sent her "sincere condolences" to the victims' relatives.

Masked gunmen armed with automatic rifles were heard shouting "Allahu Akbar" - God is greatest - as they stormed the office before firing indiscriminately, killing a number of the publication's staff and two police officers.

The attackers also reportedly shouted: "We have avenged the prophet." No group has yet claimed responsibility for the atrocity.

Chilling footage taken by terrified witnesses from windows and on rooftops overlooking the scene showed the terrorists shooting one of their victims, who appears to be in a police uniform, in cold blood at close range as he lay already injured on a pavement of the otherwise deserted Paris street. A bullet-ridden Police Nationale vehicle was left nearby.

The black Citroen hatchback the attackers used to flee the scene was found later and is being combed by forensic investigators.

French interior minister Bernard Cazeneuve said "all the means" of the justice and interior ministries have been mobilised to "neutralise the three criminals who have committed this barbaric act".

He added that the operation will take place as quickly as possible in order to "identify the aggressors and arrest them in a way that they will be punished with the severity that corresponds to the barbaric act they have committed".

Witnesses at the magazine headquarters described a scene of carnage, with bullet holes and smashed windows.

Survivor and Charlie Hebdo cartoonist Corinne "Coco" Rey was quoted by French newspaper L'Humanite as saying: "I had gone to collect my daughter from day care and as I arrived in front of the door of the paper's building two hooded and armed men threatened us. They wanted to go inside, to go upstairs. I entered the code.

"They fired on Wolinski, Cabu ... it lasted five minutes ... I sheltered under a desk... They spoke perfect French... claimed to be from al Qaida."

Gilles Boulanger, who works in the same building, likened the scene to a war zone.

"A neighbour called to warn me that there were armed men in the building and that we had to shut all the doors," he said.

"And several minutes later there were several shots heard in the building from automatic weapons firing in all directions.

"So then we looked out of the window and saw the shooting was on Boulevard Richard-Lenoir, with the police. It was really upsetting. You'd think it was a war zone."

Le Point reported that cartoonists Jean Cabu, Stephane Charbonnier and Bernard "Tignous" Verlhac were among the dead.

Charlie Hebdo's website lists "Charb" as its publication director, and "Cabu" as artistic director.

Mr Charbonnier was included in a 2013 Wanted Dead Or Alive For Crimes Against Islam article published by Inspire, the terrorist propaganda magazine published by al Qaida.

French newspaper Le Monde reported that cartoonist Georges Wolinski had also been killed.

Charlie Hebdo's editor-in-chief Gerard Biard, who was in London at the time of the attack, spoke of his shock.

He told France Inter: "I don't understand how people can attack a newspaper with heavy weapons. A newspaper is not a weapon of war."

He said the magazine had not received threats of violence: "Not to my knowledge, and I don't think anyone had received them as individuals, because they would have talked about it. There was no particular tension at the moment."

French president Francois Hollande, who rushed to the scene of the attack, said it had left France in a state of shock. He said: "We are looking for the perpetrators of this crime.

"France is today in shock, in front of a terrorist attack.

"This newspaper was threatened several times in the past. We need to show that we are a united country. We have to be firm, we have to be strong.

"We are at a very difficult moment. Several terrorist attacks have been impeded during the previous weeks. We are threatened because we are a country of freedom.

"We fight threats and we will punish the attackers."

Prime Minister David Cameron, who described the killings as "sickening", will shortly have a "full sit-down intelligence briefing" on the Paris attack from security chiefs and the outrage would feature in his talks at Number 10 with German chancellor Angela Merkel, said Downing Street.

But there was no immediate announcement of any plans for a meeting of the PM's emergency Cobra committee to discuss the atrocity and there has been no change in the UK's threat assessment by MI5's Joint Terrorism Analysis Centre, which remains at "severe". The Foreign Office warned Britons in the French capital to "take extra care" in the light of the attack.

The French government have raised the national security alert system to "alerte attentat", the highest level, across the entire Ile-de-France region around Paris

Ms Merkel, who is in London on an official visit, condemned the shooting as "barbarous", while US president Barack Obama condemned the "horrific" attack.

Ian Hislop, editor of Britain's highest profile satirical magazine Private Eye, said the victims "paid a very high price for exercising their comic liberty".

Charlie Hebdo has launched a series of attacks on Muslim extremism and the last tweet on its profile page @Charlie_Hebdo_, sent about an hour before the shootings, included a satirical cartoon of Islamic State leader Abu Bakr al-Baghdadi.

In it he wishes everyone "good health".

The attack prompted a wave of support for the magazine and within minutes #CharlieHebdo was the top trending hashtag on Twitter as people around the world shared their horror at events unfolding in Paris. A second hashtag, #JeSuisCharlie, French for "I am Charlie", also trended as people rallied behind those killed and injured in the terror attack