Thousands of Myanmar anti-coup demonstrators hit the streets Sunday as the junta regime continued its crackdown, amid overnight raids in parts of Yangon which targeted officials from Aung San Suu Kyi's political party.

Myanmar has been in chaos since the February 1 coup which ousted civilian leader Suu Kyi from power and triggered a mass uprising opposing the military junta regime.

Wednesday was the deadliest day so far, with the United Nations saying at least 38 people were gunned down as security forces fired into crowds, shooting some protesters in the head.

The UN rights office also said it has verified at least 54 deaths since the coup -- though the actual number could be far higher -- and more than 1,700 people have been detained.

The only reports of serious injuries Sunday were a 19-year-old man shot in the jaw and a woman hit by rubber bullets in Bagan, the UNESCO World Heritage Site famed for its ancient Buddhist temples.

"One woman was shot with a rubber bullet in her left leg," a rescue team member told AFP, requesting anonymity.

Security forces opened fire near the ancient city at around 9am local time (02.30 GMT).

"There was one (19-year-old) man who was shot through the jaw and neck in Bagan," Ko Ko, a member of the Bagan rescue team, told AFP.

A state-run newspaper Sunday warned people not to join the rallies.

"The public should be careful not to get involved in the protests to prevent the future of their children being ruined," the Global New Light of Myanmar said.

- 'Willing to die' -

Yangon-based activist Maung Saungkha said there were coordinated protests across multiple cities and areas on Sunday as part of a two-day general strike.

"We are willing to die for our country," he told AFP.

"This current situation is worse (than the past regime). So do we stay under this condition or do we fight? This time we must fight to win. We believe that fighting together with the young generation will get us the victory."

On Saturday, state-run media announced that if civil servants continued to boycott work, "they will be fired" with immediate effect from Monday.

But demonstrators insist they will continue to defy authorities -- with protest activity Sunday in at least seven townships across Yangon and in five other cities and regional towns, according to Facebook live feeds.

In Yangon's North Okkalapa township, protesting took on a musical flavour with guitarists, drummers and vocalists wearing Suu Kyi t-shirts singing revolutionary songs at an impromptu concert. 

"It's important, brothers and sisters, let us unite," the crowd sang.

There was a big turn out in Mandalay -- Myanmar's second biggest city -- as demonstrators chanted: "don't serve the military, get out, get out," while sitting under umbrellas with signs saying "free our elected leaders".

That city lost another life Saturday, according to the Assistance Association for Political Prisoners, which reported 21-year-old Ko Naing Min Ko died after being shot in the leg and beaten by security forces the previous day.

The monitoring group also said people connected to the military-backed Union Solidarity and Development Party were responsible for two deaths on Saturday morning in the Magway region - a 17-year-old and an NLD party official.

In Bangkok, thousands of Myanmar migrant workers rallied outside the United Nations Office on Sunday. Many waved their country's flag and held photos of Suu Kyi in the air.

- Overnight raids -

Suu Kyi's National League for Democracy party confirmed some officials were arrested in overnight police operations.

"It's true that in some townships NLD officials were arrested. But we do not know exactly how many persons were taken or arrested," party official Soe Win told AFP.

NLD MP Sithu Maung posted on Facebook that security forces last night were searching for the party's information officer U Maung Maung but couldn't find him.

"U Maung Maung’s brother was beaten by police and soldiers and his body was held in an upside-down position while he was tortured because there was no one to arrest," the MP said.

State-run media on Sunday warned ousted lawmakers involved in a group called the Committee Representing Pyidaungsu Hluttaw -- which is claiming to be the legitimate elected government -- that they are committing "high treason" and could be sentenced to death or 22 years jail.

The junta has declared group members persona non-grata and says those who communicate with them could face seven years prison.

Meanwhile, 85 Myanmar citizens are at the border with India waiting to join about 50 others who have already crossed the frontier to flee the country's coup turmoil, Indian officials said Saturday.