JOHANNESBURG, NOV. 13 -- A long-awaited report issued today by a judge investigating dozens of murders of anti-apartheid activists over the past decade, has failed to determine whether police or army "death squads" were responsible for any of the slayings.

After nearly six months of hearings, Justice Louis Harms, who was appointed by President Frederik W. de Klerk to probe the murders, concluded that the police had never operated such death squads and that testimony by self-confessed members of such units was not reliable. Harms also recommended that prosecutors pursue only one assassination of the more than 70 brought to his attention.

The African National Congress, the nation's leading black nationalist group, charged that the results were "inexplicable" and that the evidence showed such squads have operated in the past and continue to do so.

The failure of the one-man commission to shed any light on the murders of the anti-apartheid activists was likely to reinforce the view among many South African blacks that the system of justice has not changed under a reformist president, and that de Klerk has condoned a whitewash of the security forces.

De Klerk issued a statement tonight calling for an end to "witch hunts on individuals" and for "conciliatory steps," including indemnity to those involved in a past "era of serious conflict and strife."

De Klerk appointed Harms last January to investigate alleged death-squad activity after the 1989 murder of Witwatersrand University professor David Webster sparked public outrage.

Harms was extremely critical of the army's now-defunct secret paramilitary Civil Cooperation Bureau (CCB) and its operations, saying its actions had given a bad name to the whole state security apparatus. But he concluded that there was no solid evidence that the bureau had been involved in Webster's murder.

"All that the evidence shows is that the CCB might have murdered Dr. Webster. There is, however, no prima facie evidence that elevates this suspicion to anything more than a mere suspicion," said Harms.

Harms said, however, that it was still possible that "individuals attached to the CCB killed Webster." He was sufficiently impressed with the evidence he heard to urge prosecution of former CCB members in the 1986 deaths of black lawyer Fabian Riberio and his wife, Florence.

Margaret Friedman, Webster's common-law wife who was with him when he was gunned down, said the commission had failed to achieve one of its main purposes, namely to restore public confidence in the government. It had only exposed "the tip of the iceberg" regarding CCB activities, she said.

Harms concluded that the police had never operated any "hit squads" as alleged by three former policemen, who testified that they had been involved in the death of the activist lawyer Griffiths Mxenge in 1981.

One witness, death-row prisoner Almond Butana Nofemela, gave a graphic description of how he and three colleagues stabbed Mxenge 45 times outside a stadium in Durban. Another witness was a former police captain, Dirk Coetzee, who allegedly headed the "hit squad" that killed Mxenge.

But Harms concluded Nofemela had made false statements under oath before, had not told the truth in his initial affidavit and had "invented incidents in a totally false manner." Coetzee, Harms said, had "a fertile imagination," was a proven perjurer as well as "irresponsible, aggressive and impulsive," and showed "strong psychopathic tendencies."

It was possible, Harms said, that Nofemela and his colleagues had carried out Mxenge's murder as "a private enterprise" or that Coetzee had ordered the activist killed "on his own volition."

In its criticism, the African National Congress noted that Harms had been barred from investigating cross-border operations by special police and army "murder squads," which the ANC said were responsible for the killings of activists living in neighboring countries.