Police fire at several places with at least 38 people reported dead, a day after diplomats of Southeast Asian nations failed to unite behind a call for the military to release ousted leader Aung San Suu Kyi.
At least 38 protesters have been killed by Myanmar security forces, the highest number since a February 1 military coup, according to officials and local reports, as authorities extended their lethal crackdown.
The United Nations envoy to Myanmar Christine Schraner Burgener dubbed Wednesday the "bloodiest day" with 38 people dead.
"We have now more than over 50 people died since the coup started and many are wounded," she told reporters.
The previous highest total was on Sunday, when the UN Human Rights Office reported 18 dead nationwide, although other counts put it higher.
Videos from various locations showed security forces on Wednesday firing slingshots at demonstrators, chasing them down and even brutally beating an ambulance crew.
"I heard so much continuous firing. I lay down on the ground, they shoot a lot and I saw two people killed on the spot," protester Kaung Pyae Sone Tun, 23, told Reuters in Yangon city after another two protesters were killed.
Security forces continue to fire rubber bullets and tear gas to break up anti-junta protests in Myanmar, leaving dozens dead and several others wounded, a day after a regional diplomatic push to end the month-long crisis made little headway.
"My team handled the dead bodies and contacted the families" in Sagaing region, rescue worker Myo Min Tun told AFP news agency.
The deaths in Sagaing were confirmed by other medics, though it was not confirmed whether security forces used live rounds or rubber bullets.
About a two hours' drive away in Mandalay city during a different protest, a doctor confirmed two people were shot dead by security forces.
"Myo Naing Lin was shot in the chest, Ma Kyay Sin was shot in the head," he told AFP, declining to be named.
'No one wants dictatorship'
"Oh my eyes, it hurts," one woman in a teacher's uniform shouted as she and other protesters scattered through a cloud of tear gas, according to a live video feed.
Nine people were hurt when police fired rubber bullets in Mandalay, the Myanmar Now news agency reported.
There were also unconfirmed reports of firing and injuries in the central towns of Myingyan and Magway. Media reported five people were wounded in the town of Monywa.
Police dispersed crowds in the main city of Yangon with tear gas, witnesses there said.
Protesters were also out Chin State in the west, Kachin State in the north, Shan State in the northeast, the central region of Sagaing and the southern town of Dawei, media and residents said.
"We're aiming to show that no one in this country wants dictatorship," Salai Lian, an activist in Chin State, told Reuters news agency.
ASEAN meet urges restraint
Meanwhile, the foreign ministers from Southeast Asian neighbours urged restraint but failed to unite behind a call for the military to release ousted government leader Aung San Suu Kyi and restore democracy.
At least 21 people have been killed since a military coup on February 1 ended Myanmar's tentative progress towards democratic civilian rule and triggered protests across the country and international dismay.
International concern about the turmoil mounting but the Association of Southeast Asian Nations (ASEAN) failed to make a breakthrough in a virtual foreign ministers' meeting on Myanmar on Tuesday.
While united in a call for restraint, only four members, Indonesia, Malaysia, the Philippines and Singapore, called for the release of Suu Kyi and other detainees.
"We expressed ASEAN's readiness to assist Myanmar in a positive, peaceful and constructive manner," the ASEAN chair, Brunei, said in a statement.
Myanmar's state media said the military-appointed foreign minister attended the ASEAN meeting that "exchanged views on regional and international issues", but made no mention of the focus on Myanmar's problems.
It said Wunna Maung Lwin "apprised the meeting of voting irregularities" in November's election.
Ousted President Win Myint is facing two new charges, his lawyer, Khin Maung Zaw, said, including one for a breach of the constitution that is punishable by up to three years on prison.
'No more words'
The military justified the coup saying its complaints of voter fraud in the November 8 elections were ignored. Suu Kyi's party won by a landslide, earning a second five-year term. The election commission said the vote was fair.
Junta leader Senior General Min Aung Hlaing has said the intervention was to protect Myanmar's fledgling democracy and has pledged to hold new elections but given no time frame.
Singapore Prime Minister Lee Hsien Loong said on Tuesday in an interview the coup was a "tragic" step back for Myanmar and the use of lethal force by its security forc es was "disastrous".
ASEAN's bid to find a way out of the crisis has drawn criticism from inside Myanmar, with concern it would legitimise the junta and not help the country.
"No more words, action," activist Thinzar Shunlei Yi told Reuters in a message when asked about the ASEAN effort. She called for sanctions on businesses linked to the military.
'Revolution must succeed'
Tuesday evening's news bulletin on Myanmar state television said agitators were mobilising people on social media and forming "illegal organisations".
It said tear gas and stun guns grenades were used to disperse crowds in Yangon and 12 rioters were arrested.
After dark in parts of Yangon, people came to their balconies to chant anti-military slogans, including "the revolution must succeed". Others banged pots and pans in a nightly ritual of defiance.
Ye Myo Hein, a researcher and founder of Burma Studies Center, said security forces had fired shots to discourage people from taking part.
"Afterwards, a volley of pans rattling and drum beating filled the air," Ye Myo Hein posted on Facebook.
Suu Kyi, 75, has been held incommunicado since the coup but appeared at a court hearing via video conferencing this week and looked in good health, a lawyer said.
She is one of nearly 1,300 people who have been detained, according to activists, among them six journalists in Yangon, one of whom works for the Associated Press, which has called for his release.
Myanmar's representative to the United Nations, who was appointed by Suu Kyi and last week denounced the coup, has staked a claim as the legitimate representative, according to letters seen by Reuters, even though the junta fired him last week.