Putin critic and Washington Post columnist Vladimir Kara-Murza wrote from jail that hundreds of Russian anti-war protesters are being held alongside him in a new op-ed published Friday by The Washington Post.

He was arrested on Monday, the same day that he was interviewed by CNN, where he called Putin's government a regime of murderers.

When I returned home on Monday evening and began to park my car, five or six police officers of the Second Special Regiment of Moscow's Main Internal Affairs Directorate, who had been waiting at the entrance, rushed at me, hustled me into their minibus, took away.

He claimed in his most recent op-ed that his arrest was due to his anti-war position and that his sentencing process was highly political.

According to The Post, Kara-Murza survived two poisonings in the last two years. The Bellingcat investigative unit claimed that the poisoning of Kara-Murza was carried out by agents of the FSB.

No one hid it. The officers of the Khamovniki Police Department rang the doorbell when they brought me to Special Detention Center No. 2 to serve out my sentence.

Kara-Murza claimed that he spent the first day in a stone box measuring 2 by 3 meters and met other war critics, noting there were hundreds of protesters of all ages in jail for taking action against the war.

When you are told that no one is protesting against the war in Russia, don't believe it, Kara-Murza wrote.

He offered some hope in the fight against the regime of Putin and for free speech in the country.

Boris Nemtsov liked to say that Russia would be free. He wrote that he has never been so sure of it.

After Putin introduced and the Russian parliament passed a media censorship law that allows the government to jail journalists who report fake news about the military, Kara-Murza was arrested.

Private citizens can be sentenced to up to 15 years in prison if they use the word "war" publicly to describe the war in Ukraine.

Washington Post publisher and CEO Fred Ryan sent a statement to Insider saying that Kara-Murza has been relentless in his efforts to bring the truth about his country's leadership to light.

Following poisonings and other grave threats, this outrageous detention is the latest move in Vladimir Putin's effort to silence Kara-Murza and hide the truth about the atrocities Putin is committing in the Russian people's name.

The columnist's wife demanded her husband's release.

Twice the Russian authorities tried to kill my husband for advocating for sanctions against thieves and murderers, and now they want to throw him in prison for calling their war a war.