At least 44 protesters were killed Sunday as security forces cracked down on pro-democracy demonstrations, taking the death toll since the coup to more than 120, according to the Assistance Association for Political Prisoners (AAPP) monitoring group.

Myanmar has been in uproar since the putsch, with daily protests demanding a restoration of democracy despite the junta's increasingly forceful attempts to quell dissent.

The court hearing for Suu Kyi -- who spent more than 15 years under house arrest during previous military rule -- was scheduled for 10 am (0330 GMT) in Myanmar's capital Naypyidaw, but it was postponed until March 24, her lawyer Khin Maung Zaw told AFP.

"There's no court hearing because there's no internet and the hearing is conducted by video conference... We cannot do video," he said.

Myanmar authorities have throttled the internet every night for several weeks, normally restoring services in the morning, but monitoring service Netblocks said mobile data networks were kept offline Monday.

Suu Kyi faces at least four charges: possessing unlicensed walkie-talkies, violating coronavirus restrictions, breaching telecommunications laws, and intent to cause public unrest.

Military authorities have also accused her of accepting illegal payments of $600,000 in cash as well as a large quantity of gold -- allegations her lawyer says are "groundless".

Khin Maung Zaw had previously complained he was not allowed to meet Suu Kyi, who has been in custody since the coup, and on Monday said police have appointed two junior lawyers on his team to have the power of attorney.

"The police have no right to decide who represents the defendants," he said, adding that the whole situation is "strange" -- from the lack of Wi-Fi in the court to the appointment of junior lawyers.

- Martial law -

Suu Kyi's postponed hearing came a day after violent clashes between security forces and protesters, and the torching of several Chinese-owned factories in a textile-producing district of commercial hub Yangon as many protesters believe Beijing is supportive of the coup.

The AAPP on Monday said six more deaths had been confirmed to add to an overnight toll of 38, making Sunday the deadliest single day since the military seized power.

Six Yangon townships were under martial law by morning -- anyone arrested there faces trial by military tribunal rather than civilian courts, with sentences ranging from three years' hard labour to execution.

But protesters were undeterred Monday, with local media publishing images showing crowds gathering in Karen state and a sit-in protest in Myanmar's second-largest city Mandalay.

State-run television confirmed on Monday that a police officer was shot dead in the city of Bago, 60 kilometres (37 miles) northeast of Yangon, during a protest.

The Chinese embassy in Myanmar issued a statement condemning the actions of "destroyers" after the violence in Yangon's garment-producing townships, urging the police to "guarantee the security" of Chinese businesses.

Taiwan, meanwhile, advised its companies in Myanmar to fly the island's flag to avoid being targeted.

- 'Junta leaders don't belong in power' -

International alarm over the bloodshed is growing, but so far Myanmar's generals have shown no signs of heeding calls for restraint.

Tom Andrews, United Nations special rapporteur on rights in Myanmar, tweeted that he was "heartbroken/outraged" at Sunday's events.

"Junta leaders don't belong in power, they belong behind bars," he wrote.

"Their supply of cash & weapons must be cut now."

UN envoy for Myanmar Christine Schraner Burgener also condemned Sunday's bloodshed, while the country's former colonial ruler Britain said it was "appalled" by the use of force "against innocent people".

Last week, Andrews said there was growing evidence that the junta was committing crimes against humanity -- including murder, forced disappearances and torture.

Amnesty International has also accused the Myanmar military of premeditated killings and using battlefield weapons on unarmed protestors.