In the two weeks since troops ousted Aung San Suu Kyi and took the civilian leader into custody, big urban centres and isolated village communities alike have been in open revolt.

Security forces have used increasing force to quell huge nationwide street protests and a disobedience campaign encouraging civil servants to strike.

Troops have fanned out around the country in recent days and fired rubber bullets to disperse one rally in Mandalay, hours before authorities again cut internet gateways.

"They shut down the internet because they want to do bad things," said 44-year-old Win Tun, a resident of commercial capital Yangon.

"We didn't sleep the whole night so we could see what would happen."

The shutdown came after another day of protests in Yangon, in defiance of armoured vehicles and troop convoys stationed around key sections of the city -- although turnout was smaller than in recent days.

Mandalay, the country's second largest city, saw a clash that left at least six injured after police used slingshots against protesters and fired rubber bullets into the crowd.

Demonstrators retaliated by throwing bricks, according to a medic at the scene, while journalists said police had beaten them in the melee.

Crowds returned to the streets of Yangon and other locations around the country on Tuesday morning.

"I want more people to join the protests, we don't want to be seen as weak," said Thwe Ei Sann, a university student in the city.

A large crowd blocked railway tracks outside the port city of Mawlamyine to prevent a Yangon-bound train from leaving the port city.

Many of the country's locomotive drivers have joined the anti-coup work boycotts and have frustrated junta efforts to restart the national railway network after a Covid-19 shutdown.

Yangon residents had on the weekend used tree trunks to block police vehicles sent to bring striking rail workers back to their stations.

- 'Nobody believes them' -

The international community has unleashed a torrent of condemnation against the leaders of Myanmar's new army administration, which insists it took power lawfully.

UN ambassador Christine Schraner Burgener spoke to junta number two Soe Win on Monday and warned him that the regime's network blackouts "undermine core democratic principles", according to a spokesman.

State media reported the following day that the general had discussed "security measures" with the envoy, along with the regime's Covid-19 vaccination rollout and economic recovery plans.

More than 420 people have been arrested since the coup, according to a list of confirmed detentions from the Assistance Association for Political Prisoners monitoring group.

There are numerous unconfirmed reports of other arrests.

Suu Kyi and her top political ally, Win Myint, have not been seen in public since they were detained in dawn raids on February 1, the day a new parliament was due to convene.

Both are expected to appear in court by videolink in Naypyidaw this week.

The Nobel laureate, who spent years under house arrest for opposing an earlier dictatorship, has been charged under an obscure import law for possessing unregistered walkie-talkies at her home.

Her lawyer Khin Maung Zaw said he had been unable to contact his client, though officials from her National League for Democracy (NLD) party have previously said she is in good health.

UN special rapporteur Tom Andrews told AFP Monday that he does not expect Suu Kyi's court hearing to be fair.

"There's nothing fair about the junta. This is theatre. It's just theatre. And of course, nobody believes them," Andrews said.