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.
A police officer was shot at close range by a gunman as he lay injured on the pavement outside the Paris offices of satirical newspaper Charlie Hebdo, video footage shows.
The gunmen were heard shouting "Allahu Akbar" - ("God is greatest" in Arabic) - as they opened fire.
They fled the scene, reportedly shouting "We have avenged the prophet".
The men remain at large.
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.