BANGKOK/MELBOURNE (REUTERS, AFP) - Dr Sean Turnell, an Australian economic adviser to Myanmar's Aung San Suu Kyi, said in a message to Reuters on Saturday (Feb 6) he was being detained, days after she was overthrown in a coup.

"I guess you will soon hear of it, but I am being detained," he said.

"Being charged with something, but not sure what. I am fine and strong, and not guilty of anything," he said, with a smile emoji.

He later told the BBC that he had been confined to his hotel.

"Everyone's being very polite... but obviously I'm not free to move or anything like that," he said.

Attempts to contact Dr Turnell by phone were unsuccessful earlier Saturday.

This is the first known arrest of a foreign national in Myanmar since the army generals seized power alleging fraud in a Nov 8 election that Ms Suu Kyi's National League for Democracy (NLD) won in a landslide.

Australia's foreign ministry was not immediately available to comment.

Dr Turnell is a professor of economics at Macquarie University in Sydney and has been advising Ms Suu Kyi on economic policy for several years.

Macquarie University said it was aware of reports of Dr Turnell's arrest, adding it fully supported "both his work in Myanmar and the efforts of the Australian Government to secure his swift release".

A senior NLD member, who asked not to be named, said Dr Turnell had earlier ceased his work advising Ns Suu Kyi on the South-east Asian nation's economy.

On Saturday, several thousand protesters gathered in Australia's second-largest city of Melbourne denouncing the coup and demanding the release of Ms Suu Kyi.

Television and social media footage showed people wearing the red colour of the NLD, carrying portraits of Ms Suu Kyi and singing "We Won't Be Satisfied Until The End Of The World", the Burmese language anthem from the country's 1988 pro-democracy uprising, brutally put down by the military government.