S. African black towns on brink of unrest?

Sporadic black unrest in a small South African township 65 miles from Johannesburg appears to have subsided after nearly a week of disturbances. But black leaders are warning the government that the signals coming from Tumahole are more serious than the sum total of the rocks and tear gas exchanged there.

Political frustration, particularly among youth, combined with severe economic hardship have pushed black communities to a point where ''virtually anything will trigger off disturbances,'' says Bishop Desmond Tutu of the South African Council of Churches.

''I believe a very disastrous situation is developing in this country, especially after what I have seen in (the Tumahole township),'' agrees Patrick Lekota of the United Democratic Front, an antigovernment, mostly black political umbrella group.

Trouble began in Tumahole, a township serving the white community of Parys, on July 15 when 1,000 or so blacks marched through the streets in protest against rent increases and a recent rise in South Africa's general sales tax to 10 percent.

Outdoor political gatherings are illegal in South Africa and police told the protesters to disperse. The confrontation turned into rioting and looting, with police using tear gas and sjamboks (leather whips) to disperse the crowd.

Conditions in the township have remained tense all week, with blacks stoning the police and the police maintaining a heavy armed presence.

Adding to the tension, it was disclosed Wednesday that Bonakele Ngalo, a young black man from Tumahole, had died earlier in the week while in police custody.

Mr. Ngalo's arrest had nothing to do with the township unrest, according to the South African police. They say he was picked up in Parys for drunkenness.

But suspicion has been aroused that Ngalo's death was the result of police abuse. Mr. Lekota, who was detained in Tumahole July 15, claims while at the police station he saw a black man being beaten by police. Lekota says he is ''certain,'' after checking the description of the man and his clothing with Ngalo's family, that the man was Ngalo.

The South African police have denied assaulting Ngalo and say they have made an arrest in connection with his death.

Tumahole, like most black townships in South Africa, is a poor community struggling with rising unemployment and rising costs. Like most townships, it is being told by Pretoria to govern itself and make itself financially self-sustaining. This puts local black leaders in a situation of having to increase rents and service costs.

The apparent trigger to Tumahole's unrest was a recent hike in rents from about $18 per month to $26. Lekota said this increase was ''impossible'' for many residents, who he says typically earn only $70 per month.

Police said the initial demonstration in Tumahole was by youths age 10 to 20, implying economic grievances may not have been the key complaint. Lekota insists ''the average worker'' took to the streets. Twenty-six citizens are charged with public violence.