The German television channel ZDF said this was a bureaucratic trick, rather than a message to Moscow. The German Interior Ministry reportedly confirmed this.
Berlin Police spokesman Martin Halweg said that they had been alerted to a possible threat to Navalny's life, although he did not identify the source.
"If we have information about a threat to a particular person, their life, an outside threat, we take protective measures. There is a special commissariat for this. It determines what measures are to be taken," he said.
Halweg said he could not share the details of what protection the Russian was receiving but added the measures usually ranged from street patrols to in-person protection. The measures do not have a deadline.
Navalny was moved to Berlin from a Siberian city of Omsk after falling ill on a flight to Moscow. He is in a coma.