Born two years ago amid bright hopes for democratic rule in black Africa, Zimbabwe is increasingly turning back to the repressive methods of white Rhodesia to stamp out dissent.

"It's like a replay of a nightmare," a veteran civil rights lawyer said gloomily. His fellow white colleague nodded wearily in agreement and added, "We're back to square one."

Both men had risked careers and had been socially ostracized for years because of their efforts to prevent the oppression of blacks under the white regime of former prime minister Ian Smith. They had welcomed the advent of black rule under Prime Minister Robert Mugabe in 1980 in this southern African nation formerly known as Rhodesia.

Now they found themselves listing the alleged human rights violations perpetrated by the Mugabe government using the same emergency regulations put on the books by Smith: arbitrary arrests; torture; detentions without trial, access to legal assistance or even notification of families, and brutality of soldiers toward villagers in rural areas believed to be harboring armed dissidents.

The two men and most other critics, both black and white, acknowledge emphatically that so far the extent of human rights violations under Mugabe is much less serious than during the Smith regime, which executed hundreds of black opponents and detained thousands, sometimes for 10 years or more. Others note that repression is much worse in neighboring South Africa. But the trend is serious, the critics say.

The deterioration in human rights has been an outgrowth of antigovernment activity, mainly in southwestern Matabeleland Province, where an estimated 2,000 dissidents who claim loyalty to opposition leader Joshua Nkomo, despite his disavowals, have killed scores of people, staged numerous robberies and kidnaped six foreign tourists.

No overall detention figures have been released, but Sydney Sekeramayi, the minister of state in charge of the Army, said 425 dissidents have been held in Matabeleland. It is believed that between 100 and 200 persons are held in the Harare area for alleged antigovernment activities.

Estimates of those detained under Smith range between 2,000 and 3,000.

There is little question that the government has reason to feel threatened, both from internal and external foes. It has suffered armed attacks, sabotage and threats in recent months. Mugabe's party headquarters in Harare was destroyed by a massive bomb in December, and his residence was attacked in June. About 2,000 troops have spent the past 10 weeks in a vain search for the tourists kidnaped in July.

The government has detained hundreds of people in Matabeleland and elsewhere without charge. It has undermined the judiciary by refusing to abide by a court order and criticizing verdicts. It has reinstated the death penalty, which had been suspended since independence.

The vast majority of the prisoners are black, but the outcry has usually centered around white detainees, who generally have better access to the legal machinery because of their economic advantages.

A government official discounted growing Western criticism, saying it had only arisen when whites were detained.

Sen. Garfield Todd, the last moderate white prime minister of Rhodesia, who was himself detained for more than five years by the Smith government, recently told Parliament of "a fear which is shared by all. No one," he said, ". . . can be confident that his color, his name or his party affiliation can guarantee his personal safety."

A senior black official in the Ministry of Education and Culture, Toby Moyana, disclosed to the Herald daily newspaper that he had been arrested in a hotel bar by an Army officer and held for six hours without any reason being given. While in prison, he said, he saw many incarcerated soldiers.

How, he asked, does such a person have "so much power that he can send a civilian like myself to detention for no reason whatsoever?"

A black columnist who uses the pen name "Zingizi" wrote in the Sunday Mail, "I, too, and every thinking Zimbabwean would like, in fact are entitled, to know the answer to this question."

Noting the threats to the government, he nevertheless said he could "not subscribe to the idea that, in order to preserve freedom, all methods, fair or foul, are permissible, such as detaining anyone without rhyme or reason."

Such criticism in the newspapers, run by a trust in which the government has controlling interest, is rare. There is none on the government-owned radio and television.

Critical diplomats here are not willing to have their embassies identified, but in London this week the Foreign Office said Britain has expressed "very serious concern" over the detention and alleged torture of Air Force personnel, some of whom are British citizens. A Foreign Office spokesman said British Defense Minister John Nott had raised the matter last month while on a visit to Zimbabwe during which he met with Mugabe.

One diplomat here familiar with such complaints to the government said officials "do not react too well" to the criticism.

Continued deterioration of the human rights situation could eventually endanger Western aid, some said, but one diplomat acknowledged, "Given the arguments for continuing aid, it would have to get a lot nastier" before a cutback would be considered. Zimbabwe is one of Africa's major recipients of assistance with pledges of about $2 billion in grants and loans, mainly from the West, for development and rehabilitation from the seven-year war for black-majority rule.

The target for much of the criticism is the minister of home affairs, Herbert Ushewokunze.

The controversial minister has attacked the country's courts, saying they were "gravely frustrating" the work of the police and appeared to be "sowing seeds of a revolt against the government and encouraging" the dissidents in Matabeleland.

He is reportedly creating his own special police force and has been responsible for several arbitrary arrests. He refused to obey a court order to release two white farmers who were acquitted of charges of harboring weapons of war. They were finally released when Mugabe intervened.

A black official defended Ushewokunze, saying he was a political necessity for Mugabe. Many voters' sons and husbands "were detained by Smith and nobody came around and asked them what they thought about it," the official said.

"People will think Mugabe is a white man in disguise" if he does not act against alleged white opponents, he said, and added that Ushewokunze takes care of that need.

"We are at a stage of history where the United States was after independence," the American-educated official said, noting that constitutional rights were abused then mainly because of fear of far-off Britain.

However, he added, "we are doing it in a different setting," noting that there are "enemies" within the country and on the borders, a reference to South Africa. A South African military unit was discovered inside Zimbabwe in August, although South African officials said it was not on an "authorized" mission.

Another defender of Ushewokunze said many whites "will do anything they can to frustrate black rule" and noted that "there are still people in the police and courts who sympathize with the old order."

One human rights lawyer who fought the Smith regime said that the situation, although discouraging, is a far cry from the days of the white government that fought to prevent black rule.

"If you can put the information before the prime minister, Mugabe will act," he said. "It's not an ideal situation," he acknowledged, but under Smith that avenue was never available.

Under Smith, the lawyer said, blacks "could be picked up and held incommunicado, tried in closed courts, convicted, imprisoned and executed. The family often was not even notified of the execution in advance but simply told to come pick up the body."

Even those who were simply detained without trial, like Mugabe and Nkomo were for 10 years, became nonpersons. It was forbidden to mention their names in the media.

Today, as lawyers force the issue, prisoners in urban areas have been given access to lawyers and are informed broadly of their alleged offenses within seven days.

However, the Smith regulations, though somewhat modified, still allow for indefinite detention.

Court hearings are often closed, preventing publication of alleged violations of rights.

Fewer than two dozen of the current prisoners are believed to be white. The most prominent are a member of Parliament and three senior Air Force officers held in connection with the sabotage of 13 Air Force planes by explosives in July.

Two of the officers' lawyers have charged that they were tortured. Attorneys for the member of Parliament, Wally Stuttaford, allege that he was mistreated. In July a court ruled that his detention since December had been illegal but he was then arrested and charged with plotting to overthrow the government.

Most members of Mugabe's Cabinet were detained during Smith's rule. The collective total of time served is probably several hundred years.

Therefore, they do not regard "a month in the cooler as a terribly serious affair," a Western diplomat said.

To defend the current detentions on the basis of the past, however, "is a fallacious argument," he maintained. "They fought a war to end" such abuses, he said.