The latest sentence handed down by the closed court takes the total jail time the Nobel laureate and democracy figurehead is facing to two decades.

She was "sentenced to three years' imprisonment with hard labour", a source with knowledge of the case said, adding that Suu Kyi, 77, appeared to be in good health.

Detained since a putsch last year, Suu Kyi had already been convicted of corruption and a clutch of other charges by a closed junta court and sentenced to 17 years in prison.

Journalists have been barred from proceedings in the military-built capital Naypyidaw and her lawyers have been prevented from speaking to the press.

A junta spokesman did not respond to a request for comment.

The military alleged widespread voter fraud during the November 2020 election, won resoundingly by Suu Kyi's National League for Democracy (NLD), although international observers said the poll was largely free and fair.

The military has since cancelled the result and said it uncovered more than 11 million instances of voter fraud.

Last month, junta chief Min Aung Hlaing said the military was being "lenient" on Suu Kyi and could have taken "more serious actions" against her.

Myanmar was plunged into crisis following the military's power grab last year, with swathes of the country ravaged by fighting and the economy in freefall.

More than 2,200 people have been killed and over 15,000 arrested in the military's crackdown on dissent since it seized power, according to a local monitoring group.

- 'Eradicate for good' -

"These closed door hearings make it difficult to see how any of the sentencing of Aung San Suu Kyi can be credible," said Manny Maung, Myanmar researcher at Human Rights Watch.

"The ever mounting convictions... show just how depraved the Myanmar junta is."

"I can't see them sending to Suu Kyi to a labour camp," said independent Myanmar analyst David Mathieson.

But he added: "No act of violence or torture is off limits, and Suu Kyi is the nemesis they (the military) want to humiliate and eradicate, for good."

The junta declared a state of emergency after ousting Suu Kyi's government, and has previously said elections would be held and the state of emergency lifted by August 2023.

In a speech broadcast last month, Min Aung Hlaing did not mention a date for fresh polls but said they could only be held when the country was "peaceful and stable".

He also said "reform" to the electoral system was needed, including combining the first-past-the-post system -- under which Suu Kyi's NLD has won sweeping majorities -- with proportional representation.

Last month, the junta-stacked Union Election Commission said the country's 92 registered political parties would have to ask for permission if they wished to meet foreign organisations or individuals.

"Political parties need to respect the law," the commission said.

"If they fail to do so their party's registration will be dissolved."