As the military helicopter arched out of the blue summer sky to land on a huge cross chalked upon a grassy field, hundreds of fists shot up in a defiant black-power salute. Rocks were thrown at passing vehicles, police dogs snarled at protesting black youths and a cordon of riot police kept the uproar a safe distance from the chopper.

It was not the kind of reception usually given to someone about to get the key to a city. But the guest of honor, South African Cabinet minister Piet Koornhog, smiled gamely and never looked back at the disturbances as he lept from the helicopter into this black ghetto.

The minister of black affairs' visit here yesterday to receive his civic honor quickly became a highly political event with somber overtones of the deep conflicts in this diveded society.

The day began ominously with a protest by black dissidents. At 5:56 a.m., two explosions ripped away a section of the Soweto railway that transports some 200,000 black workers daily to white-owned businesses in Johannesburg.

The damage caused a delay of several hours in the morning train traffic. The explosives were Soviet-made. Pamphlets printed by the African National Congress, an outlawed guerrilla organization and the country's oldest black nationalist movement, were found at the scene, police said.

As workers boarded buses to go to work a few hours later, black youths began stoning the vehicles in an attempt to enforce a strike as a protest against Koornhof's visit. Police used dogs, riot sticks and tear gas to disperse the crowds.

Later in the morning a group of women demonstrated outside the offices of the Soweto community council, protesting an increase in rents for their government-subsidized housing.

Throughout the day, crowds sporadically stoned buses and delivery trucks, shouting, "Power is ours." One man was killed when a bus was struck and went out of control, hitting him. A woman was admitted to a hospital with a bullet wound and three policemen were injured.

When Koornhof arrived at the offices of the Soweto community council, police set up a protective circle around the building. Inside, council chairman David Thebelhali called the 55-year-old minister the "redeemer of Soweto" and praised his efforts to provide electricity, more telephones and more jobs. "Mr. Average is seeing what is being done," Thebehali said.

Koornhof took up that theme, inveighing against "wolves who are now coming in among you here, some of whom are at this very moment outside this building.

"I come here with love in my heart and friendship to assist you and my deeds prove it," he said.

"I'm here against the wishes and advice of many people telling me, 'You cannot go there.' I told them, 'Come hell or high water, I will be there in Soweto.' Only death will part me from these principles I hold dear," Koornhof declared as the booms of exploding tear-gas cannisters punctuated his words.

Through the open windows, barking dogs and shouting riot police could be seen containing the crowd. The middle -aged councilors, sitting placidly in their flowing black robes, pulled out handkerchiefs to blow their noses and wipe their eyes as the tear gas wafted in.

Ignoring the melee outside, Koornhof made a plea to the youth of Soweto to come forward and help build it up rather than "break it down." When he urged them to work with their "responsible leaders" he touched on the basic reason for yesterday's unrest -- a fundamental disagreement between the people of Soweto and the national government on who is the community's leaders are.

The community council that conferred the "freedom of the city" on Koornhof was elected by 6 percent of the potential voters shortly after the riots of 1976-77.

Many blacks refuse to recognize the legtimacy of the council, seeing it as part of the apartheid system that retains political power in white hands.

One of the council's critics, Nthato Motlana, whose civic association had called for the strike and rent demonstration, is regarded as "irresponsible" by the government. When Motlana appeared briefly at the council offices yesterday, however, he was cheered by the crowds and hoisted on their shoulders. Although the demonstrators demanded that Thebehali come out to speak with them, he refused.

"He says he is our leader, yet we have been here the whole day and he has not yet come out to speak to us," said one young black. Despite such indications of the incumbents' unpopularity among the young, the government appears intent on backing these leaders. "There is no doubt you will win because right is on your side and your cause is right, so stick it out," Koornhof told the councilors.

After a short ceremony as the afternoon sun sank into the smog from Soweto's coal-burning stoves, Koornhof got into the helicopter and flew off. A demonstrator asked, "How can he be made an honorary citizen if we who live here are not even citizens?"