YANGON: Tens of thousands of people took to the streets of Myanmar's biggest city for a fifth consecutive day on Wednesday, defying a ban on protests as the military moved to tighten its grip on the country.

Crowds swarmed through Yangon demanding the release of Aung San Suu Kyi, facing down police a day after officers dispersed crowds elsewhere with tear gas and rubber bullets, and ramped up their harassment of the ousted leader's party.

The sudden escalation of force against the demonstrations sweeping the country since last week's coup prompted a fresh chorus of international condemnation after officers fired live rounds at one rally in the capital Naypyidaw.

Two people were critically wounded in the incident -- including one woman who was shot in the head. Images depicting her in the moments after she was shot were by Wednesday appearing on a huge protest banner and had been widely shared online alongside expressions of grief and fury.

"They can shoot a young woman but they can't steal the hope and resolve of a determined people," UN special rapporteur Tom Andrews said on Wednesday.

Massive crowds returned to the streets of Yangon on Wednesday, where the day before they had faced off against a phalanx of riot police standing alongside water cannon trucks near Suu Kyi's residence.

Though there were no reported clashes with authorities in the commercial hub on Tuesday, university student Khin Nyein Wai said she was still afraid.

"I still came out as I do not like the military dictatorship," she told AFP. "This is for our future."

More politicians from Suu Kyi's National League for Democracy were detained on Tuesday along with 30 others -- including a journalist from local broadcaster DVB -- at a protest in Mandalay, the Assistance Association for Political Prisoners monitoring group said.

Their arrests came as police fired tear gas at protesters in the city who were waving red NLD flags.

State media claimed that the crowd had used "obscene language" and thrown objects at police, injuring four officers, in its first direct mention of the protests since they began on the weekend.

"Therefore, the police members dispersed in accordance with the methods and laws," the state-run Global New Light of Myanmar newspaper reported, without mentioning other police confrontations elsewhere in the country.

But elsewhere the discipline of security forces appeared to be breaking down, with four officers defecting from their lines in the eastern town of Loikaw to join the anti-coup protests, according to local media reports.

Soldiers raided NLD headquarters in Yangon after night fell, but party member Soe Win told AFP that his colleagues had been prevented from intervening due to a blanket curfew imposed on the city.

The following morning he arrived on the scene to find door locks broken, computer equipment missing, server cables cut and bank documents taken from a safe box.

The military justified last week's power grab by claiming widespread voter fraud in the November polls, which saw a landslide for Suu Kyi's party.

It quickly moved to stack courts and political offices with loyalists.

In the 10 days since army chief Min Aung Hlaing ousted the Nobel laureate from power and ended a decade of civilian rule, Myanmar has been roiled by a burgeoning civil disobedience campaign and massive street protests.

Medical staff, air traffic controllers and teachers have staged strikes, while others have fronted for work while wearing red ribbons on their uniforms or posed for photos while brandishing the three-finger salute adopted by the anti-coup movement.

Protesters on the streets have called for the release of Suu Kyi -- who has not been publicly seen since she and other top political leaders were detained -- and for the generals to respect the results of the last election.

By Tuesday, a ban on gatherings and a nighttime curfew was in effect in the three biggest cities of Yangon, Mandalay and Naypyidaw, along with various other towns.

The United States, which has led international condemnation of the coup, on Tuesday renewed its call for freedom of expression in Myanmar -- and for the generals to step down.

The UN Human Rights Council has said it would hold a special session on Friday to discuss the crisis.

European Union foreign policy chief Josep Borrell warned the bloc could impose fresh sanctions on Myanmar's military, but said any measures should be targeted to avoid hitting the wider population.

New Zealand became the first country taking action to isolate the junta by suspending high-level military and political contacts with Myanmar.