Amnesty International has called the trial of another batch of alleged coup plotters in Equatorial Guinea unfair and expressed concern over allegations of torture and possible disappearances.
Authorities in the Central African country accuse 70 people of trying to topple President Teodoro Obiang Nguema on 8 October 2004.
This attempt received little attention abroad, overshadowed by a coup plot earlier last year in which dozens of foreigners were accused of being involved, including the son of former British Prime Minister Margaret Thatcher.
At the end of this month's lower-profile trial, a military court last week handed down heavy jail sentences of up to 30 years against 23 defendants who had been charged on numerous counts, including treason and rebellion stemming from the alleged October plot.
Amnesty said all but two of the defendants who appeared in court said they had been tortured.
"One man apparently had to be carried in and out of court as he was still unable to walk," the human rights group said in a statement released over the weekend. "One woman is reported to be suffering from vaginal bleeding resulting from torture."
Amnesty also criticised the fact that six of the defendants were tried in absentia, a violation of both national and international laws.
According to the human rights group, three of these defendants were not in fact outside the country, as the court alleged, but had been detained incommunicado in Malabo since their abduction from Nigeria and Benin earlier this year.
Amnesty said one of the prisoners was known to be seriously ill and called on the government of Equatorial Guinea to divulge their whereabouts and allow them visitors, legal counsel and medical treatment.
It claimed the prisoners were being held at Black Beach Prison, which it has criticised in the past as a place where human rights are routinely violated.
Obiang, who himself came to power in a 1979 coup, has gone on national radio to deny such allegations, claiming that the facility's prisoners are well treated.
Amnesty did express satisfaction that the death penalty, sought in six of the cases during this month's trial, had not been imposed but said it was nevertheless worried by what it called serious irregularities during both the trial and the detention of the accused.
"Amnesty International calls for allegations of torture to be impartially and independently investigated as a matter of urgency," the group said.
The long-ruling Obiang has repeatedly been accused of corruption and human rights violations in this small nation where the standard of living remains low in spite of it being Africa's third-largest oil producer.
While Equatorial Guinea's per capita gross domestic product is comparable to those of Switzerland and Denmark, the country ranks behind Nicaragua, Mongolia, and Egypt on the UN Human Development Index.