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.

“Moreover, I call upon the Myanmar Armed Forces and all armed groups in Myanmar to take all measures to protect civilians from harm,” he said.

According to the organization, the two staff members of the Save the Children were returning to their office after conducting humanitarian activities nearby when they were caught up in the attack in Kayah state.

Burning vehicles with charred bodies in Myanmar contain 35 bodies of civilians after a massacre by government troops. Al-Jazeera photo

Inger Ashing, Save the Children’s chief executive, said in a released statement, “Violence against innocent civilians including aid workers is intolerable, and this senseless attack is a breach of International Humanitarian Law.”

“This is not an isolated event. The people of Myanmar continue to be targeted with increasing violence, and these events demand an immediate response,” Ashing added.