Kremlin critic Alexei Navalny was given a last minute ultimatum by his home country Russia on Monday (December 28): Fly back home at once or face jail.
Navalny - a leading opponent of President Vladimir Putin - collapsed on a plane in August and was airlifted to Germany for treatment soon after.
Western nations allege he was poisoned with a Novichok nerve agent.
Russia said it has seen no evidence he was poisoned and denied any involvement in the incident.
On Monday, Russia's Federal Prison Service - or FSIN - accused Navalny of violating the terms of a suspended sentence he is still serving from 2014.
They also said he had evaded the supervision of Russia's criminal inspection authority.
It used an article from British medical publication The Lancet about Navalny's treatment.
It said he had been discharged from hospital in Berlin on September 20th and that all symptoms of what it called his illness had vanished by mid-October.
Navalny is serving out a suspended three-and-a-half-year prison term over a theft case, a conviction he says was politically-motivated.
His probation expires on December 30th.
In a statement, the prison service warned Navalny's suspended sentence could be changed to a real jail term.
It gave no deadline for his return, but Navalny posed a screenshot of a message to his lawyer which he said he had until 9 a.m. Tuesday (December 29) to return and show up at a Moscow office.
His spokeswoman said on Twitter it was impossible for Navalny to return in time and that he was still recuperating after his poisoning.