At least 50 people have been killed across Myanmar after security forces opened fire on protesters, according to local media reports.
The deadly tally is said to include 13 in the country's second-biggest city, Mandalay, nine in the nearby region of Sagaing and seven in the commercial capital Yangon.
Dr Sasa, the disbanded democratic parliament's special envoy to the UN, said: "Today is a day of shame for the armed forces."
The shootings came as a rebel leader told Sky News that Myanmar's armed ethnic groups will not stand by and do nothing if the military continued to kill demonstrators.
People had taken to the streets again to protest against the 1 February coup, in defiance of a warning that they could be shot "in the head and back", as the junta celebrated Armed Forces Day.
The protesters refer to the public holiday by its original name, Resistance Day, to mark the beginning of a revolt against Japanese occupation in the Second World War.
This year's event was seen as a flashpoint, with protesters threatening to bolster their public opposition to the coup with more and bigger demonstrations.
After leading a military parade in the capital Naypyitaw, the junta's leader General Min Aung Hlaing repeated that his regime would hold "a free and fair election" and hand over power afterwards, but gave no timetable.
In a live broadcast on state TV, he said: "The army seeks to join hands with the entire nation to safeguard democracy.
"Violent acts that affect stability and security in order to make demands are inappropriate."
The number of people killed in the unrest since the overthrow of Aung San Suu Kyi's elected government now stands at around 380.
Source: Sky News
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