"Four of the top former surviving Khmer Rouge cadre were charged with war crimes in Cambodia by a U.N.-backed war crimes tribunal for their role in the late 1970s genocide that left nearly one-quarter of the country's population dead, the court said Thursday. The four also face charges of genocide, crimes against humanity and offences under the Cambodian Criminal Code 1956, including murder, torture and religious persecution. The accused are Nuon Chea, acting prime minister under the Khmer Rouge, who also was known as Brother No. 2; Ieng Sary, the Khmer Rouge's deputy prime minister; Ieng Thirith, the regime's minister of social affairs and action; and Khieu Samphan, head of state. ""The charges are officially brought against the accused,"" co-investigating judge You Bunleng said at a news conference on the outskirts of Phnom Penh. The indictment was signed Wednesday. "