A pile of freshly printed posters lies in the hall of the Civil Liberties Organisation in Lagos. Under the heading "Why are these people being detained?" are pictures of six prominent civil rights activists: Abdul Oroh, the organisation's director; Dr Beko Ransome-Kuti, Shehu Sani and Sylvester Odion-Akhaine of the Campaign for Democracy; Chima Ubani of Democratic Alternative; and Dr Tunji Abayomi, chairman of Human Rights Africa.
All six men were detained this year under a decree of the military regime and have not been seen since. Dr Ransome-Kuti is the only one to have been charged. He has been sentenced by a military tribunal to 15 years for possession of information about an alleged coup plot earlier this year which few Nigerians believe existed. The other men are held without charge, no one knows where, and have been allowed no access to lawyers. Beneath the six pictures is an ominous black square with the caption, "Several others".
The sham trial and recent execution of the writer Ken Saro-Wiwa and eight other minority rights campaigners is the most flagrant and visible abuse of human rights in Nigeria. Their fate demonstrated the contempt with which the military government regards civil rights in a country that was until not so long ago considered one of the most advanced in Africa. Civil rights activists hope the death of Saro-Wiwa will at least focus world attention on the crisis gripping Nigeria.
Rights have been steadily eroded during the last dozen years of military rule. Under a decree of 1984, people may be held without charge for repeated six-month periods, in effect indefinitely. To this power, known as Decree Two, the regime has resorted more and more.
It has got worse since General Sani Abacha took power two years ago, says Tunde Olugboji of the Lagos-based Constitutional Rights Project (CRP). "There are now hundreds of people being held in detention without charge. There is no category of Nigerian exempt from the decree."
Those held include rights campaigners, students, union leaders and democracy activists. The numbers can suddenly rise, as they did last year when an oil strike was brutally crushed and its organisers arrested.
Mr Olugboji fears he could be taken in at any time. He carries a minimum of campaign documents. Meetings are held at secret locations. Since the execution of Saro-Wiwa, the CRP has received more intimidating telephone calls than usual. It has been judged prudent to move the more sensitive files out of the office.
"The Abacha regime is an extremely repressive one and becoming more so all the time," says Ayo Obe, a lawyer with the Civil Liberties Organisation. "You can't tell where or when the hammer is next going to fall. In that sense the criteria under which people are arrested, detained or prevented from travelling abroad are arbitrary. Having a high profile, as was seen with the case of Ken Saro-Wiwa, is no guarantee of security," Mrs Obe says.
In this regard, the military government has been remarkably successful: most political opposition has been suppressed or bought out. Chief Moshood Abiola, the man widely believed to have won the annulled 1993 election, is still in jail facing a charge of treason.
Only a few voices dare speak out. One is Gani Fawehinmi, a lawyer and founder of the National Conscience Party. His offices were attacked last year and he has been detained so many times that he always keeps a packed bag at his side. In it are a change of clothes, toothbrush and soap. But no shoes or book, though he likes to read: they are not allowed in prison.
"I'm not optimistic about the future." he says. "Abacha's programme for transition to civil rule in three years is a ruse. He has no intention of handing over power."
Only two demonstrations have been mounted in Lagos following the Saro- Wiwa execution. Most people are too frightened. The memory of July 1993 is still fresh: 150 protesters were shot during a peaceful demonstration against the regime of General Abacha's predecessor, General Ibrahim Babangida, who annulled the June 1993 election. It was Gen Abacha, as Minister of Defence, who gave the order to shoot.
"If it's quiet here, it's the silence of the grave," says the Campaign for Democracy's Frederick Fasheun, sitting in the house of his colleague, Dr Ransome-Kuti, of whom he has not had word since he was sentenced to 15 years in jail. "This is not a country under the rule of law, it is a police state."
Nigeria retains a vibrant press, but journalists live in the knowledge that they too can be arrested at any time. Four reporters are serving 15-year jail terms for sedition.
Nigeria has been under military rule for more than 25 of the past 35 years. A succession of soldiers have dishonoured their promises to hand over to civil rule. The only one who stood down voluntarily, General Olusegun Obasanjo, is one of 40 alleged coup plotters facing long prison sentences. That 15 of them were spared execution by General Abacha on 1 October was seen as a reason for hope. But expressions of hope are no longer widely voiced today.