Myanmar's anti-coup protesters returned to the streets in force yesterday, staging the biggest demonstrations since troops fanned out around the country to quell opposition to the new military junta.

Much of the country has been in open revolt since the military deposed Nobel laureate Aung San Suu Kyi's government at the start of the month and charged her under an obscure import law.

UN special rapporteur Tom Andrews warned that soldiers going into Yangon, as had been reported, could lead to the situation there spiralling out of control.

"We could be on the precipice of the military committing even greater crimes against the people of Myanmar," he said.

Tens of thousands rallied in Yangon, some blockading roads with vehicles to stop security forces from moving around the nation's biggest city.

Police and soldiers were spotted near a key protest junction but appeared to be hanging back, looking on as demonstrators streamed past.

Yesterday's crowds came in defiance of violent efforts by the regime to bring resistance to heel -- including use of tear gas and rubber bullets -- following nationwide street protests and a disobedience campaign encouraging civil servants to strike.

Demonstrations over the past two days had been noticeably smaller since troops were deployed around Yangon at the weekend.

But social media platforms had been flooded with calls for a show of force by protesters in the hours before the junta imposed a third consecutive overnight internet blackout.

By noon, there were anti-coup demonstrations across Myanmar, from the remote highland region of Chin state to a small town in the Irrawaddy delta where parading protesters hoisted Suu Kyi posters.

After her detention in a dawn raid on February 1, Suu Kyi was charged with possessing unregistered walkie-talkies found in her home.

Her lawyer Khin Maung Zaw told AFP on Tuesday she was also charged with violating the country's disaster management law. Further details of that charge have not been made public.

The disaster management law has also been used against deposed president Win Myint for an election campaign event that the junta claims broke coronavirus restrictions.

Her lawyer added that Suu Kyi and Win Myint, both of whom he has yet to have any contact with, were expected to appear via video link during a March 1 trial.

More than 450 people have been arrested since the coup, according to the Assistance Association for Political Prisoners monitoring group.