BANGKOK—The humanitarian group Save the Children said Tuesday it has confirmed that two of its staff were among at least 35 people, including children, who were killed in eastern Myanmar on Christmas Eve in an attack it blamed on the country’s military. It said the two staff members were caught up in the attack in Kayah state as they were traveling back to their office after conducting humanitarian activities in a nearby community. “Violence against innocent civilians including aid workers is intolerable, and this senseless attack is a breach of International Humanitarian Law,” the group’s chief executive, Inger Ashing, said in a statement. “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 said. The army seized power in February, ousting the elected government and arresting top officials. Its action was met by nonviolent nationwide …