Ousted Myanmar democracy figurehead Aung San Suu Kyi is in "strong spirits", her son told AFP Tuesday after receiving a letter from her -- their first communication since she was detained in a coup three years ago.

Suu Kyi was detained on the morning of the February 2021 coup that ended a 10-year experiment with democracy and plunged the Southeast Asian nation into bloody turmoil.

The Nobel laureate, 78, has since been jailed for more than 20 years by a junta court following what rights groups say was a sham trial designed to remove her from politics.

"She is in strong spirits as always," Kim Aris said of the letter he received from his mother thanking him for a care package he had sent to her late last year.

The letter received in early January was "the first real indication I've had... that she's actually alive", he told AFP by phone from London.

"She was sending her love to all the family."

Suu Kyi, who remains hugely popular in Myanmar, has been largely hidden from view since the coup, appearing only in grainy state media photos taken during court proceedings.

Local media reported during her months-long trial that Suu Kyi had suffered dizzy spells, vomiting and at times had been unable to eat because of a tooth infection.

Her National League for Democracy (NLD) party accused the junta last September of endangering her life by denying her medical care.

Suu Kyi was continuing to suffer from dental problems, Aris told AFP, adding he had sent medicine and foods rich in vitamins in the care package.

He said she was still being held at a specially constructed compound in the military-built capital Naypyidaw.

The compound had no air conditioning in the searing heat and the concrete cells leaked during the monsoon, Australian economist Sean Turnell, who was detained there for months, told AFP last year.

Turnell, an economic adviser to Suu Kyi's government, was a co-defendant at one of her trials and later jailed before being pardoned and deported. "She was incredibly strong throughout" their trial, he said.

"She was, I think more concerned to keep the spirits up of the people, like me, charged alongside her, than she was about her own situation."

- Isolated -

Confinement in the isolated capital is a far cry from the years Suu Kyi spent under house arrest during a previous junta, where she became a world-famous democracy figurehead.

During that period, she lived at her family's colonial-era lakeside mansion in the commercial hub Yangon and regularly gave speeches to crowds on the other side of her garden wall.

Local media have reported that the house -- the subject of a dispute between Suu Kyi and her brother -- will be put up for auction in the coming weeks.

The NLD has been decimated in the junta's bloody crackdown on dissent, with one former lawmaker executed in Myanmar's first use of capital punishment in decades.

The junta dissolved the party in March last year for failing to re-register under a tough new military-drafted electoral law, removing it from polls it has indicated it may hold in 2025.

Myanmar has been in turmoil since the coup. A military crackdown on dissent has killed more than 4,400 people and seen more than 25,000 arrested, according to a local monitoring group.