French President Francois Hollande and other dignitaries held a special ceremony Sunday to honor all those killed in Islamic extremist violence around Paris in 2015 — a year when the European way of life was targeted time and again with deadly consequences.

At least one attacker is at large, and France's top security official acknowledged Sunday that authorities don't know his whereabouts. The country is under a state of emergency after attacks in Paris on Nov. 13. Paris was again jolted Thursday when a man wearing a fake explosives vest and wielding a butcher's knife ran up to a police station and was shot to death by officers standing guard.

Hollande and Paris Mayor Anne Hidalgo unveiled a plaque Sunday in memory of victims targeted at satirical newspaper Charlie Hebdo, a kosher market, a rock concert, cafes, a stadium and elsewhere. The violence left some 150 victims dead, and several attackers were also killed.

The ceremony took place at Place de la Republique, a plaza that has become a symbol of Parisians' solidarity since the attacks, which began Jan. 7, 2015 with the Charlie Hebdo attack.

French rocker and national icon Johnny Hallyday joined the army choir in a special, somber musical performance.

Interior Minister Bernard Cazeneuve called for national unity and insisted the government is doing all it can to protect France.

Many questions remain about the Nov. 13 attacks, including how many people were involved and may still be at large.

Cazeneuve said on i-Tele television Sunday that "We don't know where Salah Abdeslam is," referring to a fugitive gunman. Abdeslam crossed into Belgium Nov. 14 and Belgian authorities believe he hid out in a Brussels area apartment used to make bombs for the Paris attacks before moving on.

Meanwhile, acting on "concrete evidence" from French security authorities, German police on Saturday raided an apartment at a shelter for asylum-seekers in the western German city of Recklinghausen that they say had been occupied by the man who was killed by French police in Thursday's incident outside a Paris police station.

French Interior Minister Bernard Cazeneuve said in remarks Sunday that the man was also believed to have lived in Luxembourg and Switzerland. French investigators were still trying to determine the man's identity.

The incident occurred on the anniversary of the attack by two Islamic extremists on Charlie Hebdo in which 12 people were killed at the satirical newspaper's office.


David Rising in Berlin contributed to this story.