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.
US Secretary of State John Kerry has called the terror attacks in Paris "France's 9/11".
Seventeen people were killed in three days of bloodshed in the French capital last week, including police officers and staff at satirical magazine Charlie Hebdo.
Mr Kerry made the comments as he visited the kosher supermarket in Paris where four hostages were killed in an armed siege one week ago today.
He laid a wreath outside the deli in tribute to those shot dead by gunman Amedy Coulibaly, one of three men responsible for the string of attacks.
Speaking to French president Francois Hollande, Mr Kerry said:
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.