But although the protesters seemed excited by the large turnout, there were also fears that it would prompt a brutal reaction from a military that seems keen to cement its hold on power.

Observers in Yangon, the country's former capital, said turnout on Wednesday was the largest in days, with tens of thousands on the streets.

Images shared online showed demonstrators participating in sit-ins near the centre, shutting down traffic in some parts of the city.

"They have a right to do so without the threat of detention or violence at the hands of the Tatmadaw. The world marches with you today!" tweeted Tom Andrews, the UN's special rapporteur for Myanmar, using the official name of the country's armed forces.

News portal Eleven Myanmar reported on a "sea of demonstrators" lashing out after the February 1 coup, with hundreds of thousands demanding that Aung San Suu Kyi be released from detention and restored to her position as de facto leader of the civilian government.

She and other leaders were detained following the coup on charges observers have called spurious, such as the improper acquisition of walkie-talkies or violations of health guidelines necessitated by the coronavirus pandemic.

In Mandalay, Myanmar's third-largest city, images shared on social media showed multiple military vehicles had appeared.

Internet access was also blocked for the third night in a row.

Nonetheless, there were still protests on Wednesday.

Andrews had earlier warned that he is worried soldiers will violently put down protests, noting that he has heard about troop build-ups outside Yangon.

Such troop movements have served as precursors to bloody crackdowns in the past.

There have already been reports about an increased military presence across the country, along with social media reports of detentions and attacks on peaceful demonstrators with water cannons and rubber bullets.

Australian Associated Press