A Belarusian opposition leader who rallied mass protests against disputed leader Alexander Lukashenko has been jailed for 18 years, BBC reported. Sergei Tikhanovsky was convicted of organising riots among other charges following a trial condemned as a sham. He planned to challenge Mr Lukashenko in the 2020 presidential election, but was detained before the vote. His wife, Svetlana Tikhanovskaya, took on Lukashenko, who claimed victory in the widely discredited poll. She claimed victory herself in the August election but, fearing for her safety, was forced into exile with her children the next day. On Tuesday, Tikhanovskaya questioned the validity of the court that tried her husband and said any sentence given to him would be "unacceptable". "I will keep defending the person I love and who became the leader of millions of Belarusians," Ms Tikhanovskaya said in a video posted to Twitter. Belarusian state news agency Belta said the verdict was delivered at a court in the south-eastern city of Gomel on Tuesday. Three other opposition figures — Mikola Statkevich, Igor Losik, Vladimir Tsyganovich — were also found guilty as part of the same trial, Belta said. Tikhanovsky is the latest prominent opposition leader to be jailed in Belarus following a brutal crackdown on dissenting voices who challenged Mr Lukashenko"s election win. Lukashenko has ruled Belarus since 1994 and defied months of protests last year as opposition politicians and activists were arrested and held in prison.