A Myanmar court has sentenced ousted leader Aung San Suu Kyi and her former economist Sean Turnel to three years in prison.

The punishment is for violating the Official Secrets Act. Suu Kyi was forced to step down as president last year after the military seized power.

A case has also been registered against Turnel, who is an Australian, for violating the immigration law.

Turnelis a Professor of Economics at Macquarie University in Sydney, Australia.

He was Suu Kyi's special economic adviser during her time in power.

He was put under house arrest days after the military coup. Australia demanded his immediate release.

He has been in detention for almost 20 months. He was arrested five days after the military takeover by security forces at a hotel in Yangon, the country's biggest city while waiting for a car to take him to the city's international airport.

He had returned to Myanmar from Australia to take up a new position as Suu Kyi's special consultant a month before his detention.

Seventy-seven-year-old Suu Kyi, who is also a Nobel laureate, has already been sentenced to 23 years in various cases. She said the allegations against her were politically motivated.

Myanmar's colonial-era official secrets act criminalizes the possession, collection, recording, publishing, or sharing of state information that is "directly or indirectly, useful to an enemy." The charge carries a maximum penalty of 14 years in prison.