Hundreds of people queued from the early hours outside UK shops selling the latest edition of French satirical magazine Charlie Hebdo.
It comes as around 10 people have been arrested and questioned over the "possible logistical support" they may have provided three gunmen who carried out last week's attacks in Paris, Agence France-Presse reports.
Ian Hislop, editor of British satirical magazine Private Eye, has said "very little seems funny today" after the deaths of 10 journalists and two policemen in a terror attack in Paris.
In a statement, Mr Hislop said the victims of the Charlie Hebdo shooting "paid a very high price for exercising their comic liberty".
He added: "I am appalled and shocked by this horrific attack - a murderous attack on free speech in the heart of Europe.
"I offer my condolences to the families and friends of those killed - the cartoonists, journalists and those who were trying to protect them."
About 7,000 French Jewish people left the country last year and have moved to Israel because they did not feel safe.
The aunt of a man killed while trying to overpower gunman Amedy Coulibaly has told ITV News her family is fearful of their future in France.
A Muslim cleric in Pakistan has held a ceremony to honour Cherif and Said Kouachi, the two men suspected of the Charlie Hebdo massacre.