U Win Htein, a senior aide to Myanmar's ousted civilian leader Aung San Suu Kyi, was sentenced to 20 years in prison for treason on Friday, AFP reported, citing his lawyer.

The former member of parliament was arrested in the aftermath of a military takeover in February. Considered Suu Kyi's right-hand man, he became the first high-ranking member of the National League for Democracy (NLD) to be sentenced after a trial. 

Win Htein's lawyer Myint Thwin said they would appeal. 

Suu Kyi faces a raft of charges that could see her jailed for decades, from illegally importing walkie talkies to flouting anti-coronavirus rules. She testified for the first time in a court on Tuesday, four months after being put on trial. 

Myanmar has been in a political crisis since President U Win Myint and State Counsellor Suu Kyi, along with other officials from the NLD, were detained by the military on February 1. Suu Kyi's supporters launched nationwide protests. 

(With input from agencies)