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

The lethal crackdown on Saturday 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 MPs, told an online forum.

Protesters burn tyres as they gather against the military coup. Photo: Getty

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.”

The deaths on Saturday would take the number of civilians reported killed since the coup to well over 400.

“This 76th Myanmar armed forces day will stay engraved as a day of terror and dishonour,” the EU delegation to Myanmar said.

“The killing of unarmed civilians, including children, are indefensible acts.”

Heartache at the funeral of a person who was killed during a demonstration against the military coup in Yangon. Photo: Getty

News reports said there were deaths in the central Sagaing region, Lashio in the east, in the Bago region, near Yangon, and elsewhere.

A one-year-old baby was hit in the eye with a rubber bullet.

In Naypyitaw, Min Aung Hlaing reiterated a promise to hold elections, without giving any time-frame.

“The army seeks to join hands with the entire nation to safeguard democracy,” he said in a live broadcast on state television.

“Violent acts that affect stability and security in order to make demands are inappropriate.”

The military has said it took power because November elections won by Aung San Suu Kyi’s party were fraudulent, an assertion dismissed by the country’s election commission.

Suu Kyi, the elected leader and the country’s most popular civilian politician, remains in detention at an undisclosed location.

Many other figures in her party are also being held in custody.

In its warning on Friday evening, state television said protesters were “in danger of getting shot to the head and back”.

It did not specifically say security forces had been given shoot-to-kill orders and the junta has previously suggested some fatal shootings have come from within the crowds.