Police said they were hunting for Aliev's traveling companion, who disappeared shortly after the killing.
The man had traveled with Aliev from Belgium to Lille on January 29, the day before Aliev was found dead.
Aliev had been under police protection in Belgium because of "threats out of Russia and Chechnya over his opposition blogging," the official told Business Insider.
French police believe that the killing of a blogger from the disputed Russian region of Chechnya in a French hotel room last week was "politically motivated," a French police official briefed on the case said.
The official said the police were now hunting for the blogger's traveling companion, who disappeared shortly after the killing.
Aliev, who vocally opposed the Chechen strongman Ramzan Kadyrov and Russian President Vladimir Putin, was found dead the next morning by hotel staff.
At least 15 people have been killed by Russian hit squads in the UK, including innocent bystanders. »