Myanmar’s ousted leader Aung San Suu Kyi has been sentenced to another three years in prison after being convicted of breaching the country’s official secrets act.

The 77-year-old was tried alongside Australian economist Sean Turnell, who was also found guilty and handed the same jail term.

Three former members of Ms Suu Kyi’s cabinet were also jailed for three years.

A legal official said the prison sentences had been passed after agreeing to speak anonymously about the case, which was closed to the public and press.

Ms Suu Kyi was detained in Naypyidaw, the capital of Myanmar, after the army seized control during a military coup on 1 February, 2021.

Mr Turnell, an associate professor of economics at Macquarie University in Sydney, worked as a special advisor to Ms Suu Kyi. He was arrested five days after the military coup and has been held for almost 20 months.

The charges are understood to have made against the five defendants on the basis of documents seized from Mr Turnell.

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State television claimed the economist had access to “secret state financial information” and tried to flee the country, although the exact details of their alleged offences have not been made public.

Both Mr Turnell and Ms Suu Kyi denied the charges when they gave evidence during a trial in August.

Australia’s foreign minister Penny Wong said: “The Australian government has consistently rejected the charges against Professor Turnell during the more than 19 months he had been unjustly detained by the Myanmar military regime.”

She added Australia will continue to advocate for his release and return.

Thursday’s sentencing comes less than a month after Ms Suu Kyi was given a three-year jail term – adding to the 17 years she was already serving for other offences including alleged election fraud.

Ms Suu Kyi, awarded the Nobel Peace Prize in 1991 for her “non-violent struggle for democracy and human rights”, has also been convicted of illegally importing and possessing walkie talkies, violating COVID restrictions, sedition and corruption.

The convictions are said to be an attempt to stop her from returning to politics.

She continues to face trial for a further seven charges under Myanmar’s anti-corruption law. Each count carries a punishment of 15 years in prison and a fine.

Ms Suu Kyi denies all allegations against her.