Hundreds of police, friends and neighbors have marched silently through a Paris suburb to honor two police officials killed by an extremist claiming loyalty to Islamic State, as authorities question suspected accomplices.

Their faces solemn and lips closed, the crowd marched Thursday from Mantes-la-Jolie, where victim Jessica Schneider worked as a police administrator, to Magnanville, where she and police commander Jean-Baptiste Salvaing were stabbed at their home Monday night.

Their 3-year-old son survived the attack, which rattled France's leadership as the country is on high alert for new extremist violence. Attacker Larossi Abballa was killed in a police raid.

Three people with links to Abballa are in custody and being questioned by anti-terrorism investigators.

French police have described growing fear after multiple attacks targeting security officers.