Morten Storm, who spied on al Qaeda for Western governments, says other such cells could be in place across Europe.
A French public television station has obtained a video of police storming a grocery store in Vincennes where a gunman took several hostages.
The loosely organized hacking group says it will target the social media accounts of “terrorists.”
The hostage situation at a kosher supermarket Friday is among hundreds of anti-Semitic incidents in France in recent years.
Other "Je Suis Charlie" rallies are planned for Beirut, San Francisco, and Glasgow.
The Yemen branch of al Qaeda claimed responsibility for the attack at weekly satirical magazine Charlie Hebdo in Paris on Wednesday.
The shootings in Paris highlight that terrorists now go for "soft" targets, but terror has always been opportunistic.
Amedy Coulibaly, who killed four people at a kosher market on Friday, had tried to break two Islamist militants out of jail.
The 26-year-old woman is the fourth suspect connected to the attack on Charlie Hebdo in Paris.
French authorities focus on stopping the recruitment of French nationals into terrorism, but the Kouachi brothers slipped through.
The real problem is not a lack of willingness by Muslim communities to assimilate to European culture, but systemic discrimination.
On Friday, as police and terrorists faced off, Paris felt like a city under siege.
Police have killed the suspect who held at least six hostages at gunpoint at a Paris supermarket. It's unclear how many hostages were rescued.
Two brothers suspected of killing 12 inside a Paris newspaper this week were killed Friday after an hourslong standoff with police.
French authorities identified Hayat Boumeddienne and Amedy Coulibaly as suspects in the seizure of a kosher deli in eastern Paris.
The suspects have taken a hostage in a warehouse and made phone contact with police, who say the suspects told them they are prepared to die.
French police found a link to Thursday's fatal shooting of a policewoman with the mass killings at the Charlie Hebdo office.
Police and security forces have closed in on the two suspects in Wednesday's attacks on Charlie Hebdo that killed 12 people.
The image, shared over 100,000 times on social media, went viral after being shared by a fake account claiming to belong to Banksy.
It remains unclear whether the official al Qaeda branch in Yemen explicitly ordered the attack on the Charlie Hebdo offices in Paris.
Critics said not republishing Charlie Hebdo’s Muhammad cartoons was a cowardly act, but free speech is a two-way street.
Muslims do not think people should have freedom of expression, wrote the Muslim cleric from London.