About 500 people had been camping out and demonstrating outside the copper mine project near Monywa since Nov. 17, CNN reported.
Protesters said they were concerned about the project's environmental impact and the land that had been claimed for it.
Khin San Hlaing, a member of parliament in the region for the National League for Democracy, said riot police cleared away all the camps and protesters, which included a mixture of local residents, students and monks.
At least one monk suffered facial burns, Voice of America reported.
The protesters had defied an order to end the protest, apparently testing the limits of new freedoms granted by Myanmar's government that took office last year, VOA said. The new government had ended years of military dictatorship and implemented laws to allow protests with permission.