The United Nations special rapporteur on human rights in Myanmar has warned of "mass deaths" from starvation and disease in the country’s east where fighting goes on between rebel groups and the junta.
In the eastern state of Kayah, clashes have escalated in recent weeks.
Locals said the military fired artillery shells that have landed near villages and the UN estimates that about 100,000 people have been displaced.
"The junta's brutal, indiscriminate attacks are threatening the lives of many thousands of men, women and children in Kayah state," Tom Andrews said in a statement posted on Twitter Tuesday.
"Let me be blunt. Mass deaths from starvation, disease, and exposure, on a scale we have not yet seen... could occur in Kayah state absent immediate action," he added.
Myanmar's military is struggling to impose order since it arrested the country's de facto leader Aung San Suu Kyi and her associates on February 1 over accusations of voter fraud in favor of her National League for Democracy (NLD) party in elections last November.
The military placed commander-in-chief Min Aung Hlaing in power and pledged to hold fresh elections in a year and hand over power to the winner, but has not set a date.
The military’s crackdown on anti-coup protests has left over 800 people dead, according to a local monitoring group.
Amid the brutal crackdown, some locals, especially in townships that have seen a high death toll, have formed "defense forces" to protect the civilians.