A local human rights group in Myanmar says the military crackdown has resulted in the deaths of more than 500 people since the coup on February 1.
Thousands of people have fled to neighboring Thailand.
Protesters in the country's largest city, Yangon, say security forces on Monday targeted them with a rocket-propelled grenade that blew apart their barricade.
No major protests have been staged in recent days in central Yangon amid the increased crackdown. On Tuesday, people burned tires and scattered garbage through the streets.
Meanwhile, the military has been hitting ethnic minority areas with airstrikes since Saturday. In the country's southeastern region, which is controlled by the ethnic Karen people, thousands have fled toward neighboring Thailand. The ethnic group says the airstrikes have killed or wounded several people.
Members of local NGOs told NHK they are concerned that there will be more casualties if the military offensive continues. They say the Thai authorities have sent more than 2000 people back to the Myanmar side.
But the Thai government says they are not sending them back and are instead supporting them and providing medical assistance.