The country has been in turmoil since a February 1 coup ousted civilian leader Aung San Suu Kyi from power and triggered mass protests against the new military junta.

The police and military have responded with an increasingly brutal crackdown on demonstrators, with more than 50 people killed and nearly 1,800 arrested.

Despite the risk, protesters rallied in parts of the commercial capital Yangon, the second-largest city Mandalay and other towns around the country.

Monday's demonstrations followed an appeal by trade unions for mass walkouts to bring the economy to a standstill.

"To continue economic and business activities as usual... will only benefit the military as they repress the energy of the Myanmar people," 18 unions said in a statement.

"The time to take action in defence of our democracy is now."

Unions are seeking to extend the impact of an ongoing "Civil Disobedience Movement" -- a campaign urging civil servants to boycott working under military rule -- which has already hit state machinery hard.

The impact has been felt at every level of the national infrastructure, with shuttered hospitals, empty ministry offices, and banks unable to operate.

The junta has warned that civil servants "will be fired" with immediate effect Monday if they continued to strike.

- Hospital takeovers -

After a restless night with security forces deployed to multiple neighbourhoods and shots heard in some areas, parts of Yangon woke to a heavy police presence.

"Police and soldiers started clearing off Kyuntaw Road in Sanchaung township. They used sound bombs to stop protesters gathering," a resident told AFP.

"They are now using a bulldozer to remove the barriers protesters have made."

Reports emerged overnight that security forces had taken over several public hospitals in Yangon.

Physicians for Human Rights said it was appalled by these moves, calling them a violation of international law.

"One eyewitness account detailed armed security forces entering and seeking to occupy West Yangon General Hospital by force," the group said, adding it had reliable information that five other Yangon hospitals were being occupied with similar situations elsewhere in Myanmar.

"Even though medical personnel vacated their government posts to initiate the civil disobedience movement, many returned to government hospitals in response to escalating violence against peaceful protestors."

- International pleas -

The coup and subsequent crackdown have drawn widespread international condemnation as well as sanctions against key military personnel.

Australia's Foreign Minister Marise Payne announced late on Sunday the country was suspending its defence cooperation programme with Myanmar, which included English language training.

Canberra is reviewing its aid programme so money is channelled away from government agencies towards not-for-profit organisations.

The United Nations Special Envoy on Myanmar Christine Schraner Burgener on Friday demanded an end to the "repression" of protesters and urged the Security Council to act.

But diplomats say the Security Council was unlikely to approve any international measures against the junta, with veto-wielding China -- historically allied to Myanmar's generals -- seen as a major obstacle.

The military, which denies responsibility for loss of life in the protests, has defended seizing power by alleging widespread electoral fraud in November's elections, which Suu Kyi's party had won in a landslide.

The Nobel laureate has not been publicly seen since she was detained as the lightning coup was launched in the early hours of February 1.