TALLINN, Estonia (AP) — Ilya Yashin, a prominent Kremlin critic who is serving an 8 1/2-year sentence for criticizing Russia’s war in Ukraine, has been moved from his prison to an unknown destination, his lawyer said Tuesday.

The statement on the Telegram messaging app by Tatyana Solomina gave no further details. However, it noted that several other figures imprisoned for criticizing the military or for alleged extremist activity because of their work with the organization of the late opposition leader Alexei Navalny also were moved.

Among them are Oleg Orlov, chairman of the Nobel Peace Prize-winning human rights group Memorial, sentenced to 2 1/2 years in February; musician Alexandra Skochilenko, serving 7 years for replacing price tags in a supermarket with messages decrying civilian deaths in Ukraine; and former Navalny regional coordinators Lillia Chanysheva and Ksenia Fadeyeva, sentenced to 9 1/2 and 9 years.

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Also Tuesday, Memorial said Germany-born Russian citizen Kevin Liik, who was sentenced to four years for allegedly providing information to German special services, has been removed from his prison.

The movements prompted speculation on social media about whether they were in preparation for some kind of a prisoner swap involving Russia, the U.S. and its allies. Kremlin critics and rights advocates have previously called for exchanges that would release Russian political prisoners.

“The situation is unique in the sense that we hear several high-profile figures are being moved at the same time,” Ivan Pavlov, a lawyer who founded Department One legal group, told The Associated Press. “Given the number, we understand that a swap is expected.”

Pavlov noted that the simultaneous disappearance of several high-profile political prisoners could mean that they are being moved to one place from where they could be flown abroad.

Two Americans are imprisoned in Russia on espionage convictions: Wall Street Journal reporter Evan Gershkovich, sentenced to 20 years in July, and corporate security executive Paul Whelan. Russian-American dual national Alsu Kurmasheva, a journalist for Radio Free Europe/Radio Liberty, convicted in July of spreading false information about the military and sentenced to 6 1/2 years.

Pavlov observed that the quick conviction and sentencing of Gershkovich and Kurmasheva also signaled a possible swap could be in the making.

Yashin is one of the few well-known Kremlin critics to stay in Russia after the start of the war. He was arrested in June 2022 in a Moscow park, convicted of spreading false information about Russian soldiers, and sentenced to 8½ years in prison.

The charge stemmed from a YouTube livestream in which he talked about civilians slain in the Kyiv suburb of Bucha. After Russian forces withdrew from the area in March 2022, hundreds of corpses were found, some with their hands bound and shot at close range.

His harsh sentence didn’t silence Yashin’s sharp criticism of the Kremlin. Yashin’s associates regularly update his social media pages with messages he relays from prison. His YouTube channel has over 1.5 million subscribers.

The convictions for extremism and war criticism are part of a Kremlin crackdown on dissent that has sharply intensified since the February 2022 start of the full-scale invasion of Ukraine.

Russian authorities often transport prisoners without prior notice to their lawyers or families and some do not surface for several weeks. Navalny in December was moved without announcement from a prison in central Russia to one above the Arctic Circle, a trip he said took 20 days. He died of unexplained causes at the prison in February.

This article first appeared on APnews.com