Russia charged opposition activist Andrei Pivovarov on Tuesday with taking part in an "undesirable" organisation, an offence which an ally said was punishable by up to six years in jail.
Pivovarov was director of Open Russia, a pro-democracy group that is linked to exiled former oil tycoon and Kremlin critic Mikhail Khodorkovsky.
Open Russia said last month it was ceasing operations in Russia to protect its staff from a crackdown on the opposition.
Pivovarov was arrested days later, after police hauled him off a plane in St Petersburg that was about to take off for Poland.
He was flown to southern Russia where a court ordered him to be held in custody for two months pending trial.
Pivovarov has said the case is politically motivated and aimed at stopping him taking part in a parliamentary election in September. The Kremlin denies the case is political.
Russia declared the London-based Open Russia group "undesirable" in 2017, in effect banning its activities.
Tatyana Usmanova, a former coordinator at Open Russia, has said the allegation against Pivovarov relates to a Facebook post from a year ago voicing support for candidates running in municipal elections. He could face up to six years in jail if convicted, she said.
Police have also opened a new criminal case against him, accusing him of failing to register one of his groups as a "foreign agent", Pivovarov's Telegram account said. That is punishable by a fine of up to 300,000 roubles ($4,150), it said.
($1 = 72.3600 roubles)
(Reporting by Tom Balmforth; editing by Timothy Heritage)
