WASHINGTON (Reuters) - The U.S. State Department on Wednesday called on the Democratic Republic of the Congo to protect civilians affected by violence in the country s east, and urged its security forces to refrain from excessive force.  Department spokeswoman Heather Nauert said the U.S. government was  dismayed  by the deaths of 30 refugees from Burundi and a Congolese soldier in the city of Kamanyola last week, adding:  The cause of the violence must be determined and perpetrators must be held accountable.   