Jailed Kremlin critic Alexei Navalny said Tuesday that he had been placed in solitary confinement for the seventh time in several months. The opposition figure, who is serving a nine-year prison sentence on charges of fraud, parole violations and contempt of court, said that he had just been released from his most recent spell in solitary confinement when officers ordered his return less than a week later.  Navalny said on his Twitter account, which is run by close associates, that he was put in solitary confinement cell the for "sweeping the exercise yard poorly and insulting Сriminal Investigator Lieutenant Neimovich by calling him 'Lieutenant Neimovich' instead of addressing him by his first name and patronymic."Navalny was placed in solitary confinement several times in August and September, following his attempts to establish a labor union for inmates at his penal colony in the Vladimir region, near Moscow.Navalny previously described his solitary cell as a "concrete kennel" where it is forbidden to see other prisoners, receive parcels and letters.Last month, the opposition leader said he had been slapped with new terrorism and extremism charges that he says could put him behind bars for up to 30 years.The 46-year-old was arrested in January 2021 upon returning from Germany, where he had been recovering from a poisoning attempt that almost killed him and that was widely believed to have been ordered by the Kremlin.