Russian police on Thursday detained opposition politician Yevgeny Roizman again, this time over a post on social media, news agencies reported.
The popular former mayor of the Urals city of Yekaterinburg is already awaiting trial on charges of "discrediting" the Russian army.
Roizman is one of the last opposition figures still in the country and not behind bars.
His lawyer Vladislav Idamzhapov confirmed to Russian news agencies that he had been detained.
He was held over sharing a post of opposition figure Alexei Navalny's foundation on social media platform VKontakte in May 2022, according to Russian media.
The Anti-Corruption Foundation was declared an "extremist" organisation in 2021, putting employees, volunteers and sympathisers at risk of prosecution.
"We immediately state that Yevgeny Roizman did not take part in this offence, as he never had a personal account on 'VKontakte' and never used this social media," his lawyer told state-run news agency TASS.
Roizman was arrested and released pending trial in August on charges of "discrediting" the army for comments on Moscow's military intervention in Ukraine.
He is facing at least three years in prison on these charges.
Roizman has already been fined three times for criticising Russia's offensive in Ukraine.
He was a lawmaker between 2003 and 2007. In 2013, he became Russia's highest-profile opposition mayor and held the position for five years.
Russia's opposition, already weakened by years of repression, has been forced into silence or exile since the beginning of the offensive.
Councillor Ilya Yashin was recently sentenced to eight and a half years in prison for spreading "false information" about the offensive, and Vladimir Kara-Murza is being tried on similar charges.