"At this time, my thoughts are with Alexei Navalny's wife and his entire family," added the Limburg bishop.
The news of his death has caused grief and shock throughout the Western world: a Siberian prison authority unexpectedly announced on Friday that the well-known Russian Kremlin critic had died in custody.
According to Russian media, the 47-year-old allegedly collapsed suddenly during a walk.
Navalny's confidants doubt this account, some even speak of a targeted killing.
Governments campaign for Navalny's release
According to people close to the prominent dissident, he still appeared to be in good health during a video broadcast on Thursday.
In recent months, however, there had been repeated reports that Navalny's health had deteriorated massively due to the adverse prison conditions.
Human rights organisations and governments around the world have been campaigning in vain for his release.
Navalny's wife, Yulia Navalnaya, appeared before the cameras at a press conference organised at short notice on the fringes of the Munich Security Conference.
With tears in her eyes, she called on the international community to hold the "terrible regime" in Russia to account.
However, she was not sure whether her husband was really dead: "I don't know whether we should believe the terrible news that we are receiving exclusively from Russian state sources." Putin and his government cannot be trusted - "they always lie".
Navalny has been in prison since 2021.
He was accused of extremism, among other things.
Several courts handed down long prison sentences against him in questionable trials.
In total, he was to spend several decades behind bars.
In 2020, Navalny was the victim of a nerve agent attack. He blamed the Kremlin for it.