The Matignon, or the Prime Minister's office, raises the security alert to its highest level in the northern region of Picardie, in addition to Paris.

British Transport Police says it has increased armed patrols at London's St Pancras station to provide reassurance to the public at the Eurostar terminal.

Image source, PA

Scotland's First Minister Nicola Sturgeon says: "Today as we see further tragic developments take place, we stand shoulder to shoulder with the people of France, united in our condemnation of yesterday's atrocity, deeply saddened by the tragic loss of life and absolutely steadfast in our defence of the fundamental freedoms that we all cherish so much."

Image source, Guy Jallay & Luxemburger Wort

Photographer, Guy Jallay, took this shot of an emotional Xavier Bettel, Prime Minister of Luxembourg, at a vigil. Photo: Guy Jallay & Luxemburger Wort

BBC Trending

One of the more shocking Twitter hashtags to take off after the Charlie Hebdo attacks was #Killallmuslims, external, which has been tweeted about 100,000 times. But its popularity is not all it seems.

BBC Trending looks into the controversial trend, which is being used on both sides of the debate. Read the article here.

@stuartf24, externaltweets, external: House to house searches reported in Crepy-en-Valois by hundreds of police where #CharlieHebdo, external suspects could be hiding

The leader of France's anti-immigration Front National delegation in the European Parliament, Aymeric Chauprade, tells the BBC that France should halt what he calls the expansion of Islam in the country: "We should stop Islamisation, we should stop the expansion of NGOs and many organisations promoting sharia law on French territory. We should consider that it's not possible now to accept radical mosques, to accept radical imams and this expansion."

Ross Douthat, blogger and New York Times columnist, has written a widely shared opinion article, external, arguing that blasphemy is necessary in order to strengthen what he calls liberal civilisation.

He says that while blasphemy can often be criticised as "pointlessly antagonizing, needlessly cruel, or simply stupid", it is necessary as a counterweight against the violence which can occur as a response to it, other wise that violence will have a "veto power" over liberal societies.

George Wypyski emails: #JeSuisAhmed was a true Muslim hero, in defending the true Islam religion which recognises freedom of speech and non-violence. He died at the hands of violent thug extremists who claim they are carrying out their attacks in the name of Islam. They're just murderers hiding behind their apparent religion.

Matt Brown in Paris emails: Barricades up and terrorist warning signs around all primary schools and the town hall in Boulogne Billancourt, Paris. Je suis Charlie posters everywhere.

Patrick Pelloux, a practising doctor and columnist at Charlie Hebdo has given a tearful interview, external to French channel i-Tele France.

He was outside the building during the time of the attack, and when he was called to come back to the office where he was needed for emergency care he thought it was a "joke".

The attack happened whilst the magazine's staffers were holding a meeting discussing racism, he adds.

"They were exceptional people," he tells the host.

Image source, youtube

Assistant Commissioner Mark Rowley, UK's Association of Chief Police Officers' National Policing Lead for Counter Terrorism, says: "We are all shocked and appalled at the tragic events in Paris which saw 12 people murdered at the offices of the magazine Charlie Hebdo by armed gunmen. A massive manhunt is under way to catch the suspects and UK police will continue to do all it can to assist our colleagues in France to help catch the people who carried out that attack."

Police officer Philippe Brinsolaro pays tribute to his brother, Franck, one of the victims of the shootings, who was a police officer guarding the magazine's editor: "My thoughts are with my brother of course, with all of my family. Now it's up to us to be strong. But if there's one thing which is remarkable, it's the sense that the police are sometimes misunderstood by the public. But we mustn't forget that what happened yesterday, whatever may happen next, a police officer, whenever it's needed will put him or herself in harm's way when the security of the country is at stake. And today I want to pay tribute to all of my colleagues, to all those who get up every day to do a difficult job."

Joel Nicholas Chua emails: #‎JeSuisAhmed‬ is much, much more profound. Ahmed was the police officer who was killed on the pavement near the magazine's office. He was of course Muslim - a Muslim who died trying to protect the staff of a magazine that revelled in insulting his religion. Charlie is no hero. Ahmed was.

Bernard Kouchner, foreign minister in the Sarkozy government, tells BBC Radio 4's World at One that only unity will deal with the threat: "It is the beginning of a new era. It is the globalisation of the fight. This is not only a European problem, certainly not. This is not only a Middle East problem, this is a new mixture of certainly barbarian behaviour. The main thing is that the Muslim people in my country, they start to realise that we have a common enemy. In the name of Islam for the moderate, in the name of freedom and solidarity in our name, we don't want any religious war. We want to resist and to defeat the terrorist."

Paul Westcott emails: Charlie Hebdo should stop offending anyone - freedom of speech is one thing but so are human rights - no to racism, sexism, intolerance, terrorism and hate crimes. Caricatures of Muhammad ARE a hate crime - wake up world and look at what you are doing - double standards.

"Real war waged not by soldiers but by dark assassins... whose calm savagery chills the blood." Reaction of the press around the world.

Le Monde reports, external that there will be several high-level crisis meetings in Paris at 14:00 (GMT), 15:30 and at 17:30.

Moussa Bourekba, French Muslim researcher on Arab Mediterranean Youth, tells BBC World Service that the far right will try to exploit the attack for its political gains: "This morning Marine Le Pen, the leader of the Front National, was asking for re-establishing or at least opening up a debate on the death penalty."

Image source, @_cypherpunks_

@_cypherpunks_ tweets, external this cartoon on his timeline with the hashtag #CharlieHebdo