JOHANNESBURG, SEPT. 19 -- President Frederik W. de Klerk tonight ordered the formation of "special investigative units" to examine allegations of police misconduct during the current wave of violence in black townships. It was the first time any South African government has responded in such a manner to persistent complaints by black leaders about the actions of the authorities.

The panels, to be led by state-appointed deputy attorneys general under Justice Minister Kobie Coetsee, "shall be charged with conducting investigations without delay and with ensuring that the criminal process takes its course expeditiously," de Klerk told a news conference in Pretoria.

There was no immediate reaction to de Klerk's announcement from the African National Congress or other black groups. But the measures appeared to constitute a significant step by the government to answer charges from the black community -- and increasingly the white media -- that the police have badly mishandled the factional fighting in townships near Johannesburg that has taken more than 750 lives since last month.

Meanwhile, Winnie Mandela, the wife of ANC leader Nelson Mandela, was detained briefly today in Thokoza township south of here after police at a roadblock found some spent cartridges in her car.

The ANC said in a statement that Winnie Mandela had been invited to Thokoza, one of the sites of recent township violence, because residents "wished to hand over a quantity of spent cartridges."

Mandela, in her first reaction to Tuesday's announcement that she is to be put on trial, said today that she welcomes the South African government's decision to take her to court on charges of kidnapping and assaulting four young black activists, one of whom was later murdered. She said a trial would give her the opportunity to clear her name and reputation.

Mandela said that while she could not comment on her case, "suffice to say I welcome the decision in the sense that at last I will be able to stand a proper trial and clear my name properly."

The ANC said today's detention of Mandela was police harassment. "Not only is the SAP {South African police} intent on curbing the normal activity of the ANC, it also wishes to limit the ANC's contribution to the ending of violence," the ANC statement said.

The ANC often has charged that the police look the other way when supporters of the black nationalist organization have been attacked by other blacks, and in some cases have sided with the attackers during the recent township violence.

"The issue of police impartiality is the biggest crisis facing the country in ending violence," the general secretary of the South African Council of Churches, the Rev. Frank Chikane, said earlier today in calling for an independent commission of inquiry to investigate charges of police misconduct in the townships. "Once you've solved that, you can address the political problems."

De Klerk listed a number of recent major violent incidents that would be investigated immediately, but said Justice Minister Coetsee would have the authority to look into any other incidents that might occur in the future. His remarks seemed to indicate that the investigative units would serve as a kind of standing monitoring mechanism of police behavior in the townships.

The president also said he was considering the appointment of an independent, "highly respected person" to investigate any charges that government institutions, agencies and individuals were abusing or exceeding their powers.

"The repulsive acts of violence and other incidents demand that every incident be investigated speedily so that the facts may be brought to light and those responsible can be brought to book without delay," he said.

"The government has committed itself to the process of negotiation, not only to seek peaceful constitutional solutions but also to deal with the causes of problems," he said.

De Klerk also announced that the government was considering the establishment of "mechanisms of communications" at the local, regional and national levels to examine "community grievances;" would give rewards of up to $40,000 for information leading to seizure of arms caches, and would offer an amnesty to individuals or groups that turned in firearms or explosives by Oct. 1.

These steps are in addition to Operation Iron Fist, initiated by police over the weekend to reinforce the police and army presence in the townships and cordon off hostels for single men and squatters camps, on which much of the recent violence has centered.

The president said that among the first incidents to be investigated will be events in the black township of Sebokeng Sept. 3, when the army opened fired on a crowd, killing 11 of 36 persons who died there that night.

Another incident to be investigated will be the massacre last Thursday of passengers riding on a train from Johannesburg to Soweto. A gang armed with shotguns, knives and machetes went on a rampage through the cars hacking 26 persons to death and injuring at least 100 other passengers.