Massive crowds joined anti-coup protests across Myanmar on Monday as workers went on a nationwide strike, demanding the release of ousted leader Aung San Suu Kyi and the return of democracy.

In the commercial capital, Yangon, some estimates on the ground put protest numbers at hundreds of thousands -- kicking off a third straight day of rallies following last week's coup.

"Down with military dictatorship" and "Release Daw Aung San Suu Kyi and arrested people," the protesters chanted as they marched in the streets.

Some held signs saying "save Myanmar" and "we want democracy" while others rode on the back of trucks singing revolutionary songs.

"This is a work day, but we aren't going to work even if our salary will be cut," one protester, 28-year-old garment factory worker, Hnin Thazin, told AFP.

Construction worker Chit Min, 18, joined the Yangon rally saying his loyalty to Suu Kyi outweighed his immediate concerns about his financial situation.

"I am jobless now for a week because of the military coup, and I am worried for my survival," he told AFP.

In Myanmar's second largest city, Mandalay, thousands had also gathered by mid morning, many waving red flags and clutching photos of Suu Kyi.

Protests were also building in the capital Naypyidaw, with many riding around on motorbikes and honking car horns, while major rallies were also reported in other townships.

Over the weekend tens of thousands of people massed on the streets across Myanmar in the biggest protests since the coup.

Myanmar's generals staged their putsch by detaining Suu Kyi and dozens of members of her National League for Democracy in pre-dawn raids on Monday last week.

The generals justified the coup by claiming fraud in last November's elections, which the NLD won in a landslide.

The junta has proclaimed a one-year state of emergency, and promised to then hold fresh elections, without offering any precise timeframe.

The coup has triggered widespread international condemnation, although neighbouring China has declined to criticise the generals.

US President Joe Biden has leading the calls for the generals to relinquish power. Pope Francis on Sunday also expressed "solidarity with the people of Myanmar", urging the army to work towards "democratic coexistence".

Online calls to protest have prompted bold displays of defiance, including the nightly deafening clamour of people banging pots and pans -- a practice traditionally associated with driving out evil spirits.

The surge in popular dissent on the weekend overcame a nationwide internet blockade, similar in magnitude to an earlier shutdown that coincided with the start of the coup.

As protests gathered steam, the junta also ordered telecom networks to freeze access to Facebook, an extremely popular service in the country and arguably its main mode of communication.

But on Sunday, live Facebook video feeds from multiple cities continued to show protesters marching through the streets.

Kyaw Zin Tun, 29, an engineer said he remembers the fear he felt growing up under junta rule during his childhood in the 1990s.

"In the last five years under democracy government, our fears were removed. But now fear is back again with us, therefore, we have to throw out this military junta for the future of all of us," he told AFP.