Belarus opposition leader Svetlana Tikhanovskaya has condemned the trial of six people, including her husband, that has begun behind closed doors.
Sergei Tikhanovsky, a blogger and former presidential candidate, was detained in March 2020.
He and five other opposition figures are accused of disorder and inciting hatred against officials.
Ms Tikhanovskaya said it was not a proper court but "personal revenge" by a leader who violently seized power.
After her husband was taken into custody, she took on President Alexander Lukashenko as a candidate herself. She claimed victory in the August election but was forced into exile with her children the next day.
Mr Lukashenko has ruled Belarus since 1994 and defied months of protests last year as opposition politicians and activists were arrested and held in prison. Sergei Tikhanovsky is one of more than 500 political prisoners held in Belarusian jails, according to human rights group Viasna.
Who is on trial?
Sergei Tikhanovsky is the most prominent of the six on trial in the south-eastern city of Gomel. The popular YouTube blogger and other leading opposition candidates were jailed last year in the run-up to the presidential vote.
Video shared online showed the six defendants being led into a cage inside their detention centre with their hands cuffed behind their backs.
My husband Siarhei Tsikhanouski is being tried today, together with Mikalai Statkevich, Ihar Losik & other bloggers & activists. Diplomats weren’t allowed into the courtroom. Siarhei is facing 15 years in jail. I don't know what to expect but definitely not justice. 1/8 pic.twitter.com/JmM0Jt4cBH— Sviatlana Tsikhanouskaya (@Tsihanouskaya) June 24, 2021
Mikola Statkevich, a well-known opposition figure, shouted "Long live Belarus!" as he was brought into the courtroom.
Igor Losik, another opposition blogger, had been working on the popular Belamova channel on the Telegram messenger app when he was detained. His job was later filled by Roman Protasevich, the dissident arrested with his girlfriend Sophia Sapega, when Belarus forced a Ryanair plane to land in Minsk last month.
Also on trial are Vladimir Tsyganovich, Dmitry Papou and Artsyom Sakau.
A hearing was also being held in the capital Minsk on Thursday, where Belarus's widely popular independent website Tut.by was being designated as extremist. The website was blocked last month and many of its staff were detained.
In a separate development, the European Union imposed a raft of new sanctions on the Belarus economy, focusing on key sectors including tobacco, petroleum and potash fertiliser.
Earlier this week sanctions were imposed on a further 78 Belarusians, some of whom were linked to the "forced and unlawful landing" of the Ryanair plane.
President Lukashenko furiously criticised Germany this week for joining the Western sanctions against Belarus. On the 80th anniversary of the launch of Adolf Hitler's Operation Barbarossa against the Soviet Union, he said the sanctions were part of a "hybrid war" against Belarus and "we did not expect Germany's participation in this collective conspiracy".
His strongest words were reserved for German Foreign Minister Heiko Maas. "Who are you? A repentant German... or the heir of the Nazis?" he said.