Ex-Police Officer Held in Slayings in S. Africa : Apartheid: He is a suspect in the deaths of two prominent white activists. Authorities look for a possible rightist assassination squad.

JOHANNESBURG, South Africa--A former police sergeant has been arrested in the assassinations earlier this year of two prominent white anti-apartheid activists, South Africa’s Ministry of Law and Order announced Thursday, while state-run television reported that more arrests in the cases “are imminent.”

Police said the 31-year-old white suspect, who was not identified, has been held “for some time” in the shooting deaths of anthropology professor David Webster, who was slain by three men outside his Johannesburg home May 1, and lawyer Anton Lubowski, a member of the South-West Africa People’s Organization, who was killed outside his home in Windhoek, Namibia, on Sept. 12.

“It is believed the police are looking at the possible existence of a private assassination squad with strong right-wing links,” the government’s evening news program reported.

The announcement, the first break in the Webster slaying investigation, came as the national police force reeled from allegations by three former officers that an assassination squad aimed at anti-apartheid activists has been operating within its ranks for nearly 10 years. An investigation by the attorney general of those allegations was completed this week, and President Frederik W. de Klerk has promised swift action.

Human rights organizations have severely criticized the authorities’ inability to solve dozens of killings of activists over the last decade. Eleven people have been assassinated so far this year and 45 since 1984, according to the Human Rights Commission. The sophistication of those murders, the commission added, “is a clear indication of the widespread existence and activity of well-organized units or hit squads.”

Police headquarters said the suspect had not been charged and was being held for questioning under security laws allowing for indefinite detention. His incarceration, revealed by South African newspapers, had not previously been announced by the authorities “because this would have jeopardized an investigation which still has to be launched,” a police statement said.

Police said the man was discharged from the force in 1984 after he was sentenced to prison for murder and theft. He was convicted of killing a suspect during one of his narcotics investigations west of Johannesburg and was released on bail in 1986.

Webster, 43, was a human rights activists and researcher who had been studying repression in South Africa.