Gen. Sani Abacha's war against opponents of his military government has left an eerie silence over Nigeria.

After seizing power in late 1993, he dissolved state legislatures, banned political parties and prohibited government decrees from being challenged in Nigeria's courts.

He has crushed labor unions and shut down nearly 20 newspapers and magazines. His security forces have arrested dozens of activists, killed scores of Nigerians in demonstrations and are accused of systematically oppressing the Ogoni ethnic group, which has criticized the government.

"What you hear is the silence of the graveyard," said Abdul Oroh, executive director of Nigeria's Civil Liberties Organization. "It is quiet here because people are angry and feel helpless."

Rampant human rights abuses were cited by TransAfrica, the Washington-based lobbying organization, and the U.S. government last month in announcing campaigns to press Nigeria's military rulers to restore democracy in sub-Saharan Africa's most populous and potentially richest country. A State Department report this year said Abacha's government "showed little respect for human rights" in 1994.

Many Nigerian activists say they support international sanctions against the regime in part because Abacha has so successfully paralyzed opposition forces at home.

"There's such a pall of helplessness over the place that people feel like things can only get worse" unless the international community intervenes, said Sully Abu, former editor of African Guardian magazine, banned by Abacha last August. "These people don't care about public opinion here. If you don't agree with them, they blow your brains out or throw you in jail."

Over the past year, Nigeria's security forces have arrested hundreds of opponents, including prominent human rights activists and politicians, holding them from several days to as long as a year. Moshood Abiola is still being held after his arrest last summer when he declared himself president on the one-year anniversary of annulled elections that he reportedly won.

Abiola's arrest prompted a six-week strike by oil worker unions that strangled the economy in Lagos and the country's southwest. The government responded by arresting several labor leaders, some of whom are still in jail.

Last month, police detained a former head of state, Gen. Olusegun Obasanjo, an act that for many activists captured the regime's disdain for opponents. Obasanjo, who led Nigeria from 1976 to 1979, is the only military leader to relinquish power in favor of civilian rule. In recent years he has been an outspoken critic of military dictatorships across Africa.

"Here is a man who had served this country honorably, and they just arrested him and put him away like a common criminal," said Frederick Fasehun, a medical doctor and longtime human rights activist.

Ibrahim Gambari, Nigeria's ambassador to the United Nations, defended his nation's government last week, saying it "has not oppressed anyone." Activists and politicians have been arrested "because the survival of Nigeria is paramount," he said. "We had to maintain stability. These activists wanted to make political points. They were not thinking about what is best for Nigeria."

Late last month, a report by Human Rights Watch/Africa accused Nigerian security forces of murdering and raping members of the Ogoni ethnic group in southern Nigeria. The Ogoni with 500,000 members form a tiny minority of Nigeria's 90 million people. The Ogoni have alleged that pollution from oil wells on their territory has destroyed their farms, killed their fish and ravaged their health.

The report quoted unidentified soldiers acknowledging that they had raided Ogoni villages, shot residents and burned their homes.

Last year Nigerian police arrested Ken Saro-Wiwa, a prominent Ogoni activist, and charged him with murder. The State Department's human rights report said prison authorities bound Saro-Wiwa in chains, denied him medicine for a heart ailment and refused to allow him to see his physician.

Saro-Wiwa is currently being tried, but many prisoners often wait several years for a trial. Activists and lawyers charge that the delays are part of a continuing attack on the judicial system and prisoners' rights by the military government. The military has ruled Nigeria since a coup more than 11 years ago, and Abacha was considered the real power behind his two predecessors as heads of state, Gen. Ibrihim Babangida and the military-appointed civilian, Ernest Shonekan.

Last year, the government suspended writ of habeas corpus. It extended the time by which suspects must be tried from six weeks to three months, and it decreed that "no act of the federal military government may be questioned henceforth in a court of law."

In several cases, the government ignored court orders. After a federal court ordered the government to reopen a newspaper it had banned, the government closed it by decree. When a federal court told the government to release a human rights activist last November, the government shunned the ruling.

Tunde Babawale, a political scientist at the University of Lagos, said the government's crackdown has "brutalized the psyche" of Nigeria's middle class, long the source of the country's political dynamism.

"People are no longer shocked by what this government does," Babawale said. "People are indifferent. The government does what it does and gets away with it. Those who cannot go into exile must take refuge in silence."

Human rights activists, middle-class Nigerians and students say they believe outside pressure will be the catalyst that brings democracy back to the continent's most populous nation.

The State Department last month exhorted Nigeria's military to "quicken the pace of its stated efforts to return Nigeria to civilian rule" and called on the government to halt the "unwise practice of silencing critics of military rule."

TransAfrica promised a campaign of media advertisements and protests at Nigeria's embassy in Washington and called for a U.S. boycott of Nigerian oil. The United States buys 50 percent of the oil exported by Nigeria, Africa's biggest oil producer.

"I pray for" international sanctions, said Joseph Femiriye, a mechanic and driver in Lagos, Nigeria's largest state, with about 10 million people. "I know things will change when we get democracy. But these military people do not believe in democracy. They believe in guns. We need the intervention if things are going to change for the common people."

"We applaud the pressure. It is very welcome," said Beko Ransome-Kuti, executive director of Campaign for Democracy, which represents about 25 organizations opposed to Nigeria's government. "We know what role international pressure can play and has played in many countries in the past. Up until now, the international community has been very passive here."

Nigerian Ambassador Gambari, however, rebuked the United States, calling pressure campaigns shortsighted and counterproductive. Other Nigerians contend that proposed sanctions will hurt the nation's poorest people.

"We need support and understanding," he said. "Nigeria's problems are not fully understood by those who ought to know better. You cannot bring democracy overnight. You cannot export democracy. Only Nigerians can bring democracy to Nigeria."

Meanwhile, Nigeria's economy, once one of Africa's strongest, continues a precipitous decline marked by 100 percent inflation and a currency that has become virtually worthless. Per capita income dropped from $1,000 in 1980 to $250 in 1993.

Nigeria's institutions also have crumbled. Many of the schools in the nation's once-vaunted education system have dilapidated structures, poorly trained teachers and unusable equipment and books, and lack toilets. Hospitals suffer from a scarcity of doctors, a shortage of medicines and an overwhelming demand for basic services.

The fall of the economy, along with the collapse of the country's infrastructure and social institutions, has left middle-class Nigerians enraged at military rulers, whose corruption they blame for the nation's demise. A government panel last year found that the Nigerian officials could not account for $12.2 billion in oil sales made during the Persian Gulf War. Gambari declined to speculate on whether the government would accept a proposal to relinquish power by the first of next year. But "Jimmy Carter himself said that was not realistic," the ambassador said, referring to comments attributed to the former U.S. president during a visit here last month. "The important thing is not a set date. We need to be a bit patient."

At the University of Lagos, Oyeniyi Adigun, a third-year student, said he thinks that the West is meddling in Nigeria's affairs, although he supports a political and economic shake-up.

"You're talking about sovereignty and the internal affairs of another country," Adigun said. "And I think sanctions could hurt the people they're supposed to help. . . . Sanctions will affect the most downtrodden people."

Nearby, Sonore Omoyele, a student leader, said he would welcome sanctions even if the country's poorest people suffered.

"People will make sacrifices. They're already making sacrifices," the 24-year-old student said. "We know that sanctions would end. But we don't know when military dictatorship will end."