Suu Kyi has not been seen since being detained on February 1, and her appearance came as demonstrators took to the streets again across the country in defiance of an escalation of deadly force from the junta.

At least 18 people died on Sunday as troops and police fired live bullets at demonstrators in cities across Myanmar, according to the United Nations, which cited its own credible information.

Suu Kyi, 75, was already facing obscure criminal charges for possessing unlicensed walkie-talkies, as well as violating coronavirus restrictions by staging a campaign event during last year's election.

She is now also accused of a violation of communications laws as well as intent to incite public unrest, her lawyer Khin Maung Zaw said.

"We can not say for sure how many more cases Daw Aung San Suu Kyi will face in this period," he told reporters in Naypyidaw.

"Anything can happen in this country at this time."

Myanmar's ousted president Win Myint is also facing the same intent to incite public unrest charge in addition to coronavirus restriction breaches.

Suu Kyi has reportedly been kept under house arrest in Naypyidaw, an isolated city that the military built during a previous dictatorship.

The military has justified its takeover, ending a decade-long democratic experiment, by making unfounded allegations of widespread fraud in last November's national elections.

Suu Kyi's National League for Democracy won the election in a landslide.

The generals have hit Suu Kyi with two charges the international community widely regards as frivolous -- relating to importing walkie talkies and staging a campaign rally during the pandemic.

Monday's court proceedings were preliminary matters in the case, including with Khin Maung Zaw seeking to formally represent her.

- Uprising -

Hundreds of thousands of people have taken to streets regularly over the past month to oppose the coup.

While the military has steadily increased the type of force used to try to contain the uprising, beginning with tear gas and water cannons, this weekend's violence saw the biggest escalation.

One person was shot while crouching behind rubbish bins and other makeshift shields, and had to be dragged away by others, with the incident filmed by media.

AFP independently confirmed 10 deaths in Sunday's violence, although there were fears the toll could be much higher.

The Assistance Association for Political Prisoners, a reliable monitoring group, estimated that about 30 people had been killed by security forces since the coup on February 1.

On Monday, protests erupted again in multiple cities across the country, with demonstrators in Yangon using bamboo poles, sofas and tree branches to erect barricades across streets.

In one clash broadcast live on Facebook and verified by AFP, unarmed protesters fled after a volley of shots were fired.

It was not immediately clear if the security forces had fired live rounds or rubber bullets.

Hundreds of people were also arrested over the weekend with many in Yangon taken to Insein Prison, where Myanmar's leading democracy campaigners have served long jail terms under previous dictatorships.

More than 1,100 people have been arrested, charged, or sentenced since the coup, according to The Assistance Association for Political Prisoners.

One reporter was also shot with rubber bullets on the weekend while covering a protest in the central city of Pyay, their employer said.

Several journalists documenting Saturday's assaults by security forces were detained, including an Associated Press photographer in Yangon.

"We strongly condemn the escalating violence against protests in Myanmar and call on the military to immediately halt the use of force against peaceful protesters," Ravina Shamdasani, spokeswoman for the UN human rights office, said.

The United States has been one of the most outspoken critics of the junta, and Secretary of State Antony Blinken also reacted with horror after Sunday's violence.

"We condemn the Burmese security forces' abhorrent violence against the people of Burma & will continue to promote accountability for those responsible," Blinken tweeted, using the country's old name.