Lawyers for Alexey Navalny said Monday they have lost contact with the jailed Russian opposition leader, who was last known to be imprisoned in a penal colony east of Moscow, and his whereabouts are unknown, Paralel.Az reports citing CNN.

Navalny was sentenced to 19 years in prison in August, after he was found guilty of creating an extremist community, financing extremist activities and numerous other crimes. He was already serving sentences of 11-and-a-half years in a maximum security facility on fraud and other charges he denies.

Supporters of Navalny claim his arrest and incarceration are a politically motivated attempt to stifle his criticism of Russian President Vladimir Putin.

Lawyers have made several attempts to get access to two penal colonies near Moscow where Navalny, who has suffered serious health issues, was believed to be, spokesperson Kira Yarmysh said on X on Monday. They were informed that the 47-year-old was not at the IK-6 or IK-7 penal colonies, Yarmysh added.

“On Friday and throughout today, neither IK-6 nor IK-7 responded to them,” Yarmysh posted, adding that Navalny had been missing for six days. Navalny was last imprisoned in the IK-6 penal colony east of Moscow.