A deadly attack by government troops in eastern Myanmar on civilians carried out on Christmas Eve included two Save the Children charity staff members, the non-profit organization said on Tuesday.

“With profound sadness, we confirm two of our staff are among the burnt bodies found in Myanmar after an attack by the military on Xmas Eve. Both new fathers working on education for children,” the organization said in a statement posted on social media. “The UN Security Council must convene & take action to hold those responsible to account.”

Saying he was “horrified” by the results of the attack, United Nations (UN) Undersecretary-General for Humanitarian Affairs Martin Griffiths said in a statement on Sunday, “I condemn this grievous incident and all attacks against civilians throughout the country, which are prohibited under international humanitarian law.”

“I call upon the authorities to immediately commence a thorough and transparent investigation into the incident so that perpetrators can be swiftly brought to justice,” added Griffiths.