Frenchman Laurent Vinatier, arrested in Moscow at the beginning of June on suspicion of collecting information on the Russian army, will appeal against his arrest in court this Thursday morning.
Following Vinatier's arrest on 6 June, the Frenchman was remanded in custody until at least 5 August.
At an initial court hearing on 8 June, the employee of the Centre for Humanitarian Dialogue – a Swiss NGO that mediates conflicts outside official diplomatic channels – admitted that he had not registered as a "foreign agent" because he was unaware that a recent Russian law required him to do so.
But the Russian Investigative Committee also suspects him of having collected information on Russian military activities that "could be used against State security".
The suspicions have given rise to fears of more serious charges than the offence of failing to register, which carries a five-year prison sentence.
The Moscow court that organised the first hearing also indicated that Mr Vinatier's personal possessions had been "temporarily seized".
The Frenchman's arrest comes amid rising tensions between Paris and Moscow over the Ukraine conflict, and a day after a Russian-Ukrainian man was arrested in the Paris region on suspicion of planning violent act in connection with a "terrorist" organisation, operating in France.
