In a televised address to the nation, Mr Mandela appealed to his supporters and to white South Africans to stand together against 'the men who worship war' and 'move forward to what is the only lasting solution for our country - an elected government of the people, by the people and for the people.'
The ANC has called for a national stayaway from work today to enable Hani's mourners to demonstrate and hold religious services. It is the prelude to 'a rolling mass-action' campaign fraught with dangers which will culminate, as Mr Mandela announced last night, with Hani's funeral at Soweto's 80,000-capacity soccer stadium on Monday.
Addressing himself to ANC militants, Mr Mandela said: 'Any lack of discipline is trampling on the values that Chris Hani stood for. Those who commit such acts serve only the interests of the assassins and desecrate his memory.'
Mr Mandela's address was most passionate, and conciliatory, at the start: 'Tonight I am reaching out to every single South African, black and white, from the very depths of my being. A white man, full of prejudice and hate, came to our country and committed a deed so foul that our whole nation now teeters on the brink of disaster. A white woman, of Afrikaner origin, risked her life so that we may know and bring to justice this assassin. The cold-blooded murder of Chris Hani has sent shock waves throughout the country and the world. Our grief and anger is tearing us apart.'
The 'white woman' reference was to the witness to Hani's killing who, since passing on the alleged assassin's car-registration number to the police, has had to go into hiding for fear of right-wing reprisals.
More than 23,000 police and soldiers are to be deployed today in response to the demonstrations and services planned to commemorate Hani. South Africa's Police Commissioner, Johan van der Merwe, said he had information that radicals on the right and left planned acts of violence.
Yesterday, however, the country was - by the usual violent standards - calm. Attention focused on the magistrate's court at Boksburg, east of Johannesburg, where the man charged with the Hani murder made a brief appearance but was not asked to plead, and was remanded until 12 May. Polish-born Janusz Walus, 40, did not ask for bail.
Some 1,500 ANC supporters gathered outside the court amid a huge police presence, but were denied the opportunity of seeing Mr Walus. The police whisked him into the building before dawn and he was out by 8.30am. Two reporters who made it to court in time described Mr Walus, a karate expert, as tall, lean and fit-looking. Newspaper reports yesterday said that his fierce anti-Communism - Hani was also general secretary of the South African Communist Party - was a blood legacy, his family's business having been nationalised by the Communists in Poland.
It was confirmed on Monday that Mr Walus belongs to Eugene Terreblanche's Afrikaner Resistance Movement (AWB). In Boksburg yesterday two AWB members in full khaki and red-beret regalia turned up outside the magistrate's court, not 100 yards from where the ANC supporters were massed.
Both men were armed with pistols, visible in hip-holsters, but they took the precaution of standing by four uniformed policemen, with whom they chatted and cracked jokes.
One of the policeman, asked whether it was legal for these men to be displaying their weapons in public, replied that he was not sure. He would call his captain on the radio to find out. The captain duly turned up and explained that it was perfectly all right for the right-wingers to be carrying guns, but he asked them to do him the favour of hiding them under their clothing.
The ANC supporters did not react the way they might have to the AWB men, distracted as they were by police marksmen on the roof of the court building, one of whom occasionally trained his rifle on the crowd. When people below gesticulated angrily at him, he smiled, enjoying what to him seemed a good joke.
That other white people near by did not have to suffer the consequences of the crowd's angry mood was down, in large measure, to the leading ANC official present, Tokyo Sexwale. In a brief address, Mr Sexwale, who heads the ANC's Johannesburg region, echoed the entreaties of ANC leaders everywhere when he reminded the crowd that the organisation was 'rooted in non-racial democratic principles'.
The ANC fears that the Hani assassination could trigger a spate of unprecedented racial attacks. To avert such a possibility, the ANC's most senior Afrikaner, Carl Niehaus, was called upon to address the crowd. Mr Niehaus, who was imprisoned in the 1980s, made an impassioned speech full of rich Afrikaans 'r' sounds. To cheers, he declared: 'We will not rest till we find all those responsible for Chris Hani's death.'
Mr Niehaus was expressing the view, increasingly prevalent among ANC leaders, that Mr Walus was not acting on his own but was part of a broader conspiracy orchestrated by right-wing groups with links to military intelligence.