Every day for the past month, Hendrik Koornhof, a mild-mannered, gray-haired medical professor, has gone through a ritual that gives him little satisfaction or solace. The distress is plainly evident in his eyes.

He picks up the phone and dials the security police to inquire about his daughter, Hannchen. He asks when she will be released from detention. The reply is the bland one given all parents of detainees.

"We are given the assurance that she is well looked after -- physically," said Koornhof with a look and a voice that spoke of little assurance. The police never say when he can expect his daughter home.

In a country where detentions are an ongoing practice, Koornhof's parental anguish would not be out of the ordinary -- except for the fact that he is a brother of a Cabinet minister. To 26-year-old Hannchen, Black Affairs Minister Piet Koornhof is "Oom Piet," Afrikaans for "Uncle Piet."

It is the first time that such a close relative of a National Party Cabinet minister has been detained on suspicion of antigovernment actions. Earlier this year, the 20-year-old son of an opposition member of Parliament was detained for several weeks and, when released, placed under a five-year banning order that restricts his movements.

Koornhof was taken Oct. 12 from Benoni High School just outside Johannesburg, where she teaches English. Like 134 other people detained at present, she was placed under stringent security laws that allow the police to hold people for questioning for indefinite periods, cut off from family and lawyers and very often in solitary confinement.

Most of the detainees are black, but this year has seen a marked increase in the number of whites detained. Many are students at English-language universities.

In theory, South Africa's security apparatus protects the country from the sabotage and violence of underground guerrillas, who are part of the "communist onslaught." But in practice, the Afrikaner-dominated system stifles almost all political opposition to apartheid, the official policy of separation of the races.

No official reason has been given for Koornhof's detention. But it appears to be linked to the arrest of several friends and acquaintances during the last two months, including one of her housemates. Most of the detainees worked in educational or rural development projects.

Koornhof was raised in a conservative, religious Afrikaner household, but "always made up her own mind about things," according to her father. Uncharacteristically, she chose to attend an English-speaking university. And although she opposed the racial policies her uncle helps implement, Koornhof was far from being a high-profile activist, tending to make her political statements in an unobtrusive fashion. She is a member of a multiracial teachers' association set up in opposition to the segregated unions.

Separated from her husband, she lived with their 6-year-old son in a commune in a white area of Johannesburg.

"I feel hurt and humiliated because of the things that have happened to her," Koornhof's father said in an interview.

But her detention has not affected his political views "because I've always felt worried. I'm acutely aware of the tragedy of our country. There is a lot of potential and good will among all the people, including the Afrikaners. I feel very sad.

"I keep on hoping that things will change without a revolution, but as times goes on and so little does happen, one gets more and more despondent . . . ."

"We are Afrikaners and we are proud of that fact. There is nothing that worries me about our background or origins. But because of that, things which happen in this country hurt even more," the 54-year-old doctor said.

A smaller and more relaxed man that his older brother, Koornhof says they try to keep their fraternal political disagreements on an "intellectual" level.

"We're a close family and being the oldest, my brother kind of regards himself as the head of the family," Koornhof said. "We see each other three or four times a year and we call each other on our birthdays. I love my brother.

"That is the tragedy of this country, you can love a person, you can be close to a person and yet not understand the political views which make him do what he does. I know many people are hurt by his policies," Koornhof said.

Hendrik Koornhof is well aware that in the conservative millieu of Afrikaner society, his daughter is already guilty of something just because she has been detained. "I know my daughter is not a criminal, but there are some people, especially Afrikaners and especially among the right wing, who may think so," he said.

On the other hand, "people have been so good to me," he said, telling of a package that came from a black doctor he knows in the black township of Soweto. Inside, there were a sweater for himself and a dress for his wife, hand-knit by the doctor's wife. With them was a card. Koornhof could not recall the exact words, "but it was something like, 'God works in strange ways,' " he said. "That really touched me the most."