A court in Myanmar on Tuesday sentenced a leader of the Karen ethnic minority group to two decades in prison for treason, his legal adviser said, in a case that has soured peace efforts. Nyein Maung, a member of the Karen National Union (KNU) central committee, was arrested last year in China and deported to Myanmar, where he was taken into custody. A special court in Yangon’s Insein prison gave him life imprisonment — which is equivalent to 20 years in Myanmar — for high treason, said his adviser Aung Thein. Nyein Maung was handed an additional three years under the illegal organisation act but will serve the two sentences concurrently, he said. Myanmar considers the KNU — whose leadership is based in Thailand — to be an illegal organisation. Its armed wing has been waging Myanmar’s longest-running insurgency, battling the government since 1949. The KNU signed a pact with the new reform-minded government in January of this year in a move that raised hopes of a permanent end to one of the world’s oldest civil conflicts.