(Reuters) – Global outrage spread over civilian killings near Kyiv including evidence of bound bodies shot at close range and a mass grave found in areas retaken from Russian troops. WAR CRIMES INVESTIGATION? * U.S. President Joe Biden called Russian President Vladimir Putin a war criminal on Monday and said he would call for a war crimes trial. * Ukraine said 50 of some 300 bodies found in Bucha northwest of Kyiv city were victims of extra-judicial killings by Russian troops. Reuters could not verify the report. * Satellite images showed a 45-foot (14-m) -long trench dug into the grounds of a…