Navalny, 47, a former lawyer who rose to prominence more than a decade ago by lampooning President Vladimir Putin's elite and voicing allegations of vast corruption, is currently in a jail about 60 km (40 miles) north of the Arctic Circle.
Kira Yarmysh, his spokesperson said on X late on Monday that it was the 25th time Navalny had been placed in solitary confinement and that he had spent 283 days in such conditions.
Sentenced to stay in prison until he is 74 on charges he says were trumped up to keep him out of politics, Navalny said on Monday that he was being forced to listen to a pro-Putin pop singer at 0500 every morning after being played the Russian national anthem.
The Russian authorities cast Navalny as a fraudulent Western-backed extremist out to up-end political stability and sew chaos across the world's largest country, something he denies.
(Reporting by Reuters; Editing by Andrew Osborn)
