Myanmar's military rulers have threatened to jail people who take part in a "silent strike" on Tuesday, as activists urged residents to stay indoors and for businesses to close in a protest to mark the anniversary of the army seizing power.

Myanmar has been in chaos since Nobel laureate Aung San Suu Kyi and other figures from her National League for Democracy (NLD) party were rounded up in raids, accused by the junta of rigging a 2020 election the NLD won.

The overthrow of Suu Kyi's government triggered huge street protests last year, but the bloody crackdown that ensued left hundreds of civilians dead and led to the forming of "people's defence forces to take on the well-equipped army.

In recent days, activists have urged people to strike, including staging flash mob protests to get out the message, distributing pamphlets and using social media.

"We might be arrested and spend our life in jail if we are lucky. We might be tortured and killed if we are unlucky," said Nan Lin, a youth activist, who hopes the strike will send a strong message to the junta.

A group that said it was coordinating the strikes urged the international community to recognise a shadow Myanmar government and impose a no-fly zone in conflict areas and a global arms embargo on the junta.

A spokesman for the ruling military did not respond to phone calls seeking comment.

In the northern city of Myitkyina, signs put up by the military warned residents not to join the protest.

"Those who participate in the silent protest will be punished according to these laws," read a photograph of a sign posted on social media.

It listed prison terms ranging between 20 years and three years under laws on counter-terrorism, high treason, public mischief and telecommunications.

International pressure

UN Secretary General Antonio Guterres ahead of the coup anniversary urged the junta to allow greater humanitarian access.

"The multiple vulnerabilities of all people across Myanmar and its regional implications require an urgent response," said Farhan Haq, his deputy spokesperson.

The junta has accused the UN of bias and interference and is refusing to bow to international pressure, despite a corporate retreat from Myanmar and sanctions, the latest on Monday, when the United States, Britain and Canada blacklisted more individuals tied to the junta.

For ordinary Myanmar people, life has got harder with the economy tanking since the coup and with some residents describing a constant fear of being detained, regular power outages and internet curbs.

Security forces have killed at least 1,500 civilians and arrested 11,838 since the coup, according to the Assistance Association of Political Prisoners, an activist group cited by the UN. The junta disputes the death toll.

Suu Kyi, 76, is on trial in more than a dozen cases that carry combined maximum sentences of more than 150 years in prison, charges that critics say are designed to ensure she can never return to politics.

An internationally backed diplomatic effort led by the Association of Southeast Asian Nations (ASEAN) has faltered, with the junta's failure to honour its commitment to end hostilities and support dialogue frustrating prominent members, including Singapore.

"Conditions in Myanmar for the people continue to deteriorate," its foreign ministry said in a statement marking the anniversary, which demanded Suu Kyi and all political prisoners be freed.

"Singapore remains deeply concerned about the situation in Myanmar, and disappointed by the lack of progress."