International charity Save the Children has confirmed two of its staff members in Myanmar were killed in an attack it blames on the military.
More than 35 bodies, including those of women and children, were found in eastern Kayah state, the charity says.
It said troops had forced people from their cars, arresting some of them and killing others before burning their bodies.
The Myanmar military has denied the claims.
Save the Children said the two staff members killed were “both new fathers working on education for children”. They were traveling home for the holidays after conducting humanitarian work.
In a tweet, the charity called on the UN Security Council to convene and take action to hold those responsible to account.
Following the reported attack, US Secretary of State Antony Blinken said the military had to be held accountable. He also called for a ban on arms sales to the Myanmar military.
Mass protests have taken place across Myanmar (also known as Burma) since the military seized control in February.
Elected leader Aung San Suu Kyi and members of her National League for Democracy (NLD) party are among those detained.
Hundreds of people, including children, have been killed.
Photos showing the aftermath of the attack in Hpruso township have emerged in which the charred remains of vehicles are visible.
The Karenni National Defence Force, one of the largest militias opposing the junta, said the dead were not militia members but civilians seeking refuge from the conflict.
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