Opponents of a Chinese-backed copper mine in northern Myanmar have resumed their protest just weeks after a violent police crackdown on demonstrators at the site, an activist said Tuesday.

Up to 200 villagers have joined the new peaceful roadside demo, a Buddhist monk who attended the protest told AFP by telephone.

"They're demanding a halt to work by the Wanbao company while an investigation is under way, and for soil not to be dumped on their farmland," said the monk, who did not want to be named for security reasons.

Opposition leader Aung San Suu Kyi is heading a 30-member commission investigating the Monywa mine project as well as a pre-dawn raid last month that left dozens of protesting monks injured, some with severe burns.

It was not clear what had caused the demonstrators' injuries, but Suu Kyi suggested tear gas could be to blame.

It was the toughest clampdown on demonstrators since a reformist government came to power last year. The authorities have since apologised to the monks.

"The villagers are waiting for the result of the investigation. At the same time, they don't want to be forgotten," the monk said.

"That's why they have been protesting since December 12 by setting up camps by the side of the road."

Activists are calling for work at the mine -- a joint venture between Chinese firm Wanbao and military-owned Myanmar Economic Holdings -- to be suspended to allow impact studies amid claims of mass evictions and pollution.

China insists that the contentious points have already been resolved, but the dispute echoes fierce opposition to a Chinese-backed mega-dam which saw President Thein Sein suspend the scheme last year in response to public outcry.