Security services could not hope to keep close tabs on everyone with terrorist sympathies, but there were important questions to be asked nonetheless, the Royal United Services Institute's Shashank Joshi tells the BBC.

"The question isn't so much 'did they slip through?' - they certainly did - but what were the indications? Were there any indications they were acquiring weaponry, for example; that is a failure. They built up a weapons cache; there are some indications their neighbours knew about the weapons cache. The failure to have forewarning of that is a failure, but I think it is important to remember that there are hundreds and hundreds, if not thousands of people on these lists. No intelligence agency can track them all."

Image source, @MineParis81

@MineParis81 tweets, external her photo of the "Paris est Charlie" sign on the Arc de Triomphe.

#JeSuisCharlie, external is now one of the most popular hashtags in Twitter's history, says Twitter France, external.

Image source, Julia Macfarlane

Manuel Valls
French Prime Minister

"There is a clear failing. When 17 people die, it means there were cracks (in security)."

PM Valls made the comments to French channel BFMTV.

@HugoJoel9tweets, external: @BBC_HaveYourSay You can kill the messenger but you can't kill the message. je suis charlie #charliehebdo

A Moroccan man holds a sign in French and Berber during a vigil in Rabat, Morocco.

Image source, AFP

There was another candlelit vigil in Cairo, Egypt.

Image source, AP

Frank Gardner
BBC security correspondent

tweets:, external Indications are that Kouachi brothers appeared to live 'a normal life' so fooled French authorities into thinking they weren't a threat.

Jack Garland
BBC Newsnight

A difficult day in Paris, but heartening to see relieved parents picking up their kids from schools in the Porte de Vincennes area, now lifted from lockdown.

Image source, Jack Garland/BBC Newsnight

Residents are starting to return to their homes in the area of Porte de Vincennes that was earlier under siege.

Image source, Getty Images

James Longman, BBC reporter, Paris

tweets: , externalWalking through lifted siege zone. Slowly coming back to life. Strangers stop to ask shopkeepers if they are ok. Uplifting #ParisAttack

An unnamed Israeli official, quoted by AP, says 15 hostages were rescued from the Jewish supermarket in eastern Paris. The official was recounting a conversation between Israeli Prime Minister Benjamin Netanyahu and French President Francois Hollande.

US President Barack Obama tells France: "The United States stands with you." Speaking on a trip to Tennessee, he says he has been in contact with the French authorities over the Paris shootings and that he is hopeful the immediate threat is now resolved.

Image source, AP

The French president also confirmed he would be attending a unity rally in Paris on Sunday "to stand up for France's values". UK Prime Minister David Cameron, his Spanish counterpart Mariano Rajoy and German Chancellor Angela Merkel are among the European leaders expected to join the march.

Image source, AP

President Hollande has condemned the attack at the Jewish supermarket in Paris as "a dreadful anti-Semitic act".

But he said France would face further threats and that it would not give into fear. He called the gunmen "fanatics" who did not represent the Muslim faith. The French "mustn't be divided," he said.

President Hollande said he wanted to pay tribute to "the bravery and efficiency of all the police who took part in today's operations...to tell them that we are proud of them".

"They did it to save lives, and to neutralise terrorists who had committed murders."

President Francois Hollande confirms four people were killed in the Paris supermarket attack, speaking in a live televised address.

BFMTV news channel is broadcasting a telephone interview with a man who they identified as the supermarket gunman, named as Amedy Coulibaly. In the interview, he says he had been coordinating his attack with the Charlie Hebdo suspects and that he was from the Islamic State militant group active in Syria and Iraq.

But one of the Charlie Hebdo suspects, Cherif Kouachi, told the same channel he had been sent and financed by al-Qaeda in Yemen, another militant group which is not believed to have had overt ties with Islamic State.

Reports say an armed man is holding two hostages at a jewellery store in Montpellier, southern France, but there is no indication it is linked to the hostage situations in Paris.

Speaking at a press conference, Interior Minister Bernard Cazeneuve expressed his gratitude to the police and emergency services who showed "professionalism and courage", adding that the whole French nation was relieved tonight.

He said that forces would remain mobilized in order to keep all French people protected.

Here, Bernard Cazeneuve (L) is seen leaving after a crisis meeting at the Elysee Palace.

Image source, AFP