WASHINGTON (Reuters) – United Nations Secretary-General Antonio Guterres on Sunday said he was “deeply shocked” by images of dead civilians in the Ukrainian town of Bucha, and he called for an independent investigation that “leads to effective accountability.” Guterres posted his comments on Twitter a day after witnesses and officials said that Russian troops killed almost 300 civilians as they withdrew from the town near Kyiv. “I am deeply shocked by the images of civilians killed in Bucha, Ukraine,” Guterres said, joining Western officials in expressing outrage. “It is essential that an inde…