The Myanmar military's crackdown on mass anti-coup demonstrations has led to the deaths of 38 people on Wednesday, marking the deadliest day since the junta took power, the UN's special envoy for the country warned.

Christine Schraner Burgener told reporters during a virtual news conference that the killings have raised to more than 50 the number of those have who have died, and "many" others have been wounded amid ongoing mass demonstrations against the military's power grab.

Earlier in the day, police and security forces opened direct fire to disperse protesters rallying across the country against the junta. But that did not stop a large number of people from once again taking to the streets in major cities and towns to demand the restoration of civilian rule. 

Burgener said the police, who are controlled by Myanmar's military, have used 9-millimeter submachine guns to fire on protesters using live ammunition.

In all, over 1,200 people have been detained since the Feb. 1 coup d'etat with many of their whereabouts a mystery to family members, according to the UN. 

Successive states, including the US and Canada, have imposed sanctions on the junta in a bid to restore the democratically-elect government, but the Tatmadaw, as the military is formally known, has shown no signs of changing course. The US has vowed to issue harsher economic penalties, but they have yet to be unveiled. 

Burgener said that in her conversations with the military, officials brushed off the penalties, saying they "are used to sanctions, and we survived” them in the past.

"When I also warned they will go in an isolation the answer was, we have to learn to walk with only a few friends," she said. “It’s clearly up to the member states to decide what kind of measures they will take further.”

Kyaw Moe Tun, Myanmar's now-contested ambassador, issued an emotional appeal last week for the international community to act using "any means necessary" against the military junta.

"Now is not the time for the international community to tolerate the war crimes and crimes against humanity committed by the Myanmar military," said Tun, who has maintained the legitimacy of his appointment by the democratically-elected government.

Tun's role as UN ambassador was contested by the military-controlled Ministry of Foreign Affairs the day after Tun's explosive speech.

It appointed his deputy, Tin Maung Naing to fill the post, but the UN has yet to decide on who is the country's actual ambassador. /aa