The government issued banning orders on two leading black activists today in the politically volatile city of Port Elizabeth.

The move, which follows last Friday's lifting of the seven-month state of emergency in Port Elizabeth and two other major urban areas, was seen as a signal of the government's determination to enforce tight restrictions on political dissent by using its broad array of regular legal tools, rather than invoking emergency powers.

The government also announced it was withdrawing its expulsion order against three CBS television journalists. They had been told to leave after the network violated the emergency ban on televised coverage of violent conflicts. It broadcast videotape of last week's mass funeral for 17 unrest victims in the black township of Alexandra.

A joint statement quoted a CBS executive as saying the network's reporters would "as far as possible, ensure that material obtained and used by them from whatever source is not tainted with illegality."

The banning orders were served on Henry Fazzie and Mkhuseli Jack, two men who are widely considered moderating influences on the young radicals who dominate black politics in the Port Elizabeth area, a stronghold of antiapartheid radicalism.

One indication of their stature was that the orders were immediately denounced by spokesmen for the white business community.

The orders, which are effective for five years, restrict them to the Port Elizabeth area during weekdays and confine them to their homes on weekends and holidays. They are barred from attending political gatherings or from "disseminating information of a political nature."

Both were local leaders of the United Democratic Front, the largest antiapartheid coalition group. Jack, 28, is president of the Port Elizabeth Youth Congress and was spokesman for the black boycott committee that last year conducted a highly successful four-month consumer boycott of white-owned stores in the economically depressed port city. Fazzie is the front's regional vice president.

The actions were taken under the state's sweeping internal security act after Minister of Law and Order Louis le Grange made a ruling that the two men "pose a threat to the maintenance of law and order." The order said no further information would be released because it could be "detrimental to the public interest."

About 15 people currently are under banning orders, the most noted of whom is Winnie Mandela, wife of the imprisoned black nationalist leader. About 70 were effectively "banned" under the state of emergency after their release from detention, but those orders expired when the emergency was lifted last week.

Jack and Fazzie, both of whom were detained by police during last year's boycott, had been key figures in negotiations with the business community that had led to the boycott's suspension last November.

The director of the city's chamber of commerce, Anthony Gilson, said his organization reacted to the news "with shock and dismay. A carefully cultivated climate of negotiation is now in extreme jeopardy."

The president of the regional branch of the United Democratic Front, Edgar Ngoyi, said the banning orders were "grossly vindictive" and aimed at "doing away with the democratic voices of our people." He predicted that the moves would increase the likelihood that the boycott would be resumed in April, the deadline for the state to meet a number of conditions set by the black community in a mass meeting.

Police have been accused in the past of undermining local initiatives aimed at building channels of communication between white and black moderates in Port Elizabeth. Efforts to negotiate an early end to last year's boycott collapsed last July following the imposition of the state of emergency. Dozens of black leaders, including Jack and Fazzie, were rounded up or forced to go underground. The boycott dragged on for three more months, crippling the local economy.

The Associated Press quoted police in Kobokweni black township, near Mozambique, as saying they shot dead two teen-agers and wounded 81 other blacks in scattering a crowd gathered for the trial of eight blacks on riot charges.