Security forces killed more than 90 people across Myanmar on Saturday in one of the bloodiest days of protests since a military coup last month, news reports and witnesses said.

The lethal crackdown came on Armed Forces Day. Senior General Min Aung Hlaing, the junta leader, said during a parade in the capital Naypyitaw to mark the event that the military would protect the people and strive for democracy.

State television had said on Friday that protesters risked being shot “in the head and back”. Despite this, demonstrators against the February 1 coup came out on the streets of Yangon, Mandalay and other towns.

The Myanmar Now news portal said 91 people were killed across the country by security forces.

A boy reported by local media to be as young as five was among at least 29 people killed in Mandalay. At least 24 people were killed in Yangon, Myanmar Now said.

“Today is a day of shame for the armed forces,” Dr Sasa, a spokesman for CRPH, an anti-junta group set up by deposed lawmakers, told an online forum.

Meanwhile, one of Myanmar’s two dozen ethnic armed groups, the Karen National Union, said it had overrun an army post near the Thai border, killing 10 people - including a lieutenant colonel - and losing one of its own fighters.

A military spokesman did not respond to calls seeking comment on the killings by security forces or the insurgent attack on its post.

“They are killing us like birds or chickens, even in our homes,” said Thu Ya Zaw in the central town of Myingyan, where at least two protesters were killed. “We will keep protesting regardless... We must fight until the junta falls.”