Myanmar security forces fired live rounds and tear gas at protesters again on Tuesday, leaving at least three people critically injured as regional powers rebuked the junta over its deadly crackdown.

The country has seen weeks of mass protests demanding the military release civilian leader Aung San Suu Kyi, who has been in detention since the February 1 coup.

Soldiers and police have steadily stepped up their use of force, deploying tear gas, water cannon, rubber bullets and, increasingly, live rounds.

Sunday was the bloodiest day since the military takeover, with the United Nations saying at least 18 protesters were killed across the country. AFP independently confirmed 11 deaths.

Another rally turned violent Tuesday, in the northwestern town of Kale where security forces opened fire on protesters, according to medics who witnessed events and treated those wounded.

"About 20 people were injured in a morning crackdown by police and soldiers in Kale," said a rescue worker, speaking on condition of anonymity for fear of repercussions.

"Three... were hit by live rounds and are in a critical condition," he said.

Police had initially deployed tear gas and rubber bullets before doubling back with live rounds, he added.

A doctor who treated the patients in a local hospital confirmed the number of people in a critical condition.

"One was hit in his thigh and he's now under operation. Another one got hit in the abdomen and he requires blood transfusions... Another one got hit in the chest," he told AFP.

'No mercy, just bullies' 

The bloodshed came on the same day as the funeral was held in the commercial capital of Yangon for a 23-year-old student who died on Sunday.

The mourners sang a revolutionary song as the coffin carrying Nyi Nyi Aung Htet Naing moved through a sea of thousands to an altar. Some climbed trees to catch a glimpse of the procession.

"No mercy, just bullies — dead bodies are here and there,” the mourners sang in unison as they flashed a three-finger salute. "Oh, the brave heroes who died for democracy.”

Protests also continued in several neighbourhoods of Yangon on Tuesday, with demonstrators wearing hard hats and wielding improvised home-made shields.

In San Chaung township — which saw crackdowns in recent days — hundreds of police came out in force.

"They used tear gas and were shooting as well,” said one resident.

About 15 minutes away near the popular shopping area Yuzana Plaza, local media live-streamed protesters chanting as what appeared to be smoke from tear gas whizzed their way.

"We threw wet blankets to the protesters for them to cover the canisters to prevent the tear gas [from spreading],” said one resident living by the plaza, who added that she saw some demonstrators being arrested.

More than 1,200 people have been arrested, charged and sentenced since the coup, according to the Assistance Association for Political Prisoners monitoring group, of which about 900 are still behind bars.

But the number is likely far higher — state-run media reported that on Sunday alone more than 1,300 people were arrested.

A Myanmar journalist was detained overnight in the southern city of Myeik — the latest among the country’s press corps to be targeted by security forces.

Reporters Without Borders says at least 10 journalists are in jail and 26 have been arrested since the coup.

‘Not acceptable’ 

The unrest continued as foreign ministers from the 10-member Association of Southeast Asian Nations bloc held a virtual meeting which included a Myanmar representative.

Ahead of the talks, some regional powers broke with diplomatic traditions and issued unusually harsh rebukes to Myanmar’s junta.

"To use lethal force against civilians and unarmed demonstrators, I think it is just not acceptable,” Singapore Prime Minister Lee Hsien Loong told the BBC.

After the meeting Indonesia’s foreign minister Retno Marsudi expressed concern over rising violence and deaths as well as frustration over a lack of cooperation from the Myanmar regime.

"It takes two to tango. ASEAN’s good intentions and readiness will be meaningless if Myanmar does not open its door for ASEAN,” she said, adding that the restoration of democracy should be supported.

Marsudi also called for the release of political detainees.

There was no ASEAN joint communique or statement released after the meeting because the foreign ministers could not reach a consensus.

But Brunei, which chaired the meeting, issued a statement saying ASEAN called on all parties to "refrain from instigating further violence and for all sides to exercise utmost restraint”.

"We expressed ASEAN’s readiness to assist Myanmar in a positive, peaceful and constructive manner,” Brunei said.

Observers are sceptical about what difference the bloc can make, pointing to its policies of non-interference and making decisions based on consensus.