Belarus on Friday charged a former campaign staffer for Bernie Sanders and Barack Obama with allegedly organizing an illegal political rally for the candidate running against the country’s authoritarian president in Sunday’s election, his lawyer told BuzzFeed News.

Vitali Shkliarov, a 44-year-old Belarusian citizen who as the spouse of a US diplomat holds an American diplomatic passport, is being held because of “group actions that grossly violate public order," according to Shkliarov's lawyer.

The lawyer, Anton Gashinsky, said that authorities also allege Shkliarov violated the “legitimate demands of government officials, resulting in disruption of transport, enterprises, institutions, and organizations."

If convicted, Shkliarov could be fined or imprisoned for up to three years, or both, according to the criminal code under which he’s charged.

In his first communication with Western media since his detention, Shkliarov denied the charges and told BuzzFeed News through Gashinsky that he believes the charges are retaliation for his public criticism of President Alexander Lukashenko.

The jailing and indictment of Shkliarov is the latest in a crackdown by Belarus’s notoriously heavy-handed authorities ahead of Sunday’s presidential election.

Neither the State Department nor the Belarusian authorities responded immediately to requests for comment.

More than 1,300 people, including journalists and election monitors, have been detained ahead of the poll, according to the Viasna human rights group. Thirty-three Russian military contractors accused of trying to destabilize the country have also been detained.

Authorities allege that Shkliarov is responsible for organizing a May 29 event in the western Belarusian city of Grodno where popular vlogger Sergei Tikhanovsky was collecting signatures for his wife, Svetlana, to run for president.

Tikhanovsky was detained at the event and remains in jail, while his wife has gone on to build an extraordinary campaign that has rallied Belarusians who told BuzzFeed News they are hungry for change after 26 years under the iron-fisted rule of President Alexander Lukashenko.

Lukashenko has been accused by international watchdogs of human rights abuses over the course of his five terms in office. International election monitors have deemed all but his first election victory rigged. This year, the government has banned outside monitors from observing the vote.

Shkliarov runs a popular Telegram channel where he publishes analysis about political events in the US, Russia, Ukraine, and Belarus. A week before he was detained, he also blasted Lukashenko for his use of “populism and brute force” in a column published with Forbes Russia.

Shkliarov, a fluent English speaker and a self-described political junkie, is based along with his wife in Washington but makes frequent trips to Eastern Europe. His most recent campaign work came in 2018, when he served as senior adviser for Ksenia Sobchak, a Russian socialite who went on to lose the election to President Vladimir Putin.

Shkliarov worked on the 2016 presidential campaign of Sanders as director of mobilization for Nevada and on President Obama’s 2012 reelection campaign, during which he ran a team of some 40 organizers, according to CNN.

Shkliarov told BuzzFeed news through his lawyer that he was in his hometown of Gomel with his son to visit his mother, who has cancer, and his father when he was detained on July 29; he had just left the family’s home to buy a watermelon.

He said he didn’t get far before agents from Belarus’s KGB security service “kidnapped” him and hauled him to a pretrial detention center in Minsk. He had only enough time to send one word to followers of his Telegram social media channel: “Arrested.”

On July 31, the country’s deputy prosecutor general ordered Shkliarov to remain in pretrial detention, according to Gashinsky.

Since then, Shkliarov said through his lawyer, he has changed jail cells several times and endured horrific conditions. In one case, he said he was crammed into an overcrowded cell inside a damp basement with mold and cockroaches, as well as inmates who were constantly smoking.

Gashinsky has filed complaints about Shkliarov’s detention and the conditions in which he is being held but said they have been ignored by authorities.

Little had been mentioned publicly about Shkliarov in Belarus until Thursday, when Lukashenko in public remarks carried by the Belta news agency spoke about a US passport holder who had been taken into custody. “Some people were detained with American passports, married to Americans, working in the State Department,” Lukashenko said, likely alluding to Shkliarov.