"Police used water cannon to clear the (road)," Naypyidaw resident Kyaw Kyaw, who had joined the protest, told AFP.

A photographer also witnessed the incident, the first reported use of water cannon against protesters since rallies kicked off three days ago.

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

"We are joining the protest to end the military dictatorship," Kyaw Kyaw said.

Rallies over the weekend were largely peaceful, but local media reported that in the southeastern city of Myawaddy, police fired warning shots in the air to disperse a group of protesters.