African National Congress leader Nelson Mandela accused the South African government Tuesday of massacring demonstrators and causing black-on-black violence. Mandela also charged the government with defaming his wife, Winnie, in a murder and assault trial involving one of her former bodyguards, and said the ANC is not satisfied with reforms introduced by President F.W. de Klerk. Mandela, speaking to reporters after returning from an eight-nation African tour, said de Klerk has no control over the police force. He accused police of ``slaughtering'' black people involved in political demonstrations. He alleged it was government policy to keep ANC supporters fighting members of the Inkatha political organization in Natal province, where more than 5,000 people have died in the past five years. ``It is quite clear that the government does not want this violence to end,'' Mandela said. ``If the government continues to massacre our people while they are talking of negotiations, that we cannot permit. We will have to address that question specifically in relation to whether these negotiations shall continue.'' De Klerk is hoping to begin formal talks with black leaders on constitutional changes that would give the black majority a voice in national affairs _ something denied them under the current system of apartheid. Since taking office in August, de Klerk has made a number of reforms, including legalizing the long-banned ANC; freeing Mandela from a life prison term; and ending segregation of beaches and hospitals. Mandela said the ANC is not satisfied. ``We have got basic demands,'' he said. ``The most basic of these is the demand for everybody to have the right to determine his own affairs.'' Mandela said the government has deliberately besmirched his wife's name by linking her to the alleged crimes of one of her former bodyguards, Jerry Richardson, but not charging her. Richardson is charged with murder, kidnapping, attempted murder and assault. Eight other bodyguards are facing lesser charges in separate trials. Three men have testified in court that Winnie Mandela whipped them, beat them allowed her bodyguards to keep them captive in her home and assault them in December 1988 and January 1989. One of the alleged victims, 14-year-old black activist Stompie Seipei Moeketsi, was found dead Jan. 6, 1989. Mrs. Mandela denies wrongdoing and has not been charged with a crime. ``When my wife is not charged and the whole case centers on her, she has no way of defending herself,'' Mandela said. But Mandela said he was not calling on the government to prosecute his wife. ``I am saying that the way the case has been conducted is intended to defame my wife without her having the opportunity to defend herself,'' he said. It was the first time Mandela had spoken publicly on the matter in South Africa since he was freed Feb. 12 from a life prison term for sabotage and plotting the overthrow of the white-minority government.