Opposition leaders in Chad said today they were worried about a number of their colleagues arrested a week ago in the dying hours of a failed rebel assault on the capital.
Several opponents of President Idriss Deby, including former head of state Lol Mahamat Choua, were taken from their homes in N'Djamena by armed men in uniform last Sunday.
"We have no news. We can't find out where they are, or even if they are still alive," Mahamat Allahou Taher, spokesman for Mr Lol's Rally for Democracy and Progress (RDP) party said.
Chad's opposition has traditionally been vocal but politically weak compared to strong military leaders who have repeatedly seized power by force in the central African state.
The opposition is nonetheless central to hopes for a more active multi-party democracy.
No charges have been brought publicly against the opposition leaders, who include fellow parliamentarians Ngarlegy Yorongar, Mr Deby's closest challenger in a 2001 election, and Wadal Abdelkader Kamougue.
A fourth detainee, Ibni Oumar Mahamat Saleh, leads a coalition of opposition parties who opposed a 2006 constitutional referendum that allowed Mr Deby to contest a third term in office, and boycotted a subsequent election.
Asked about their whereabouts last week, Mr Deby - who seized power in 1990 in a lightning three-week offensive said: "I am on the ground to save the country, I do not deal with these details".
Some 400 Irish troops are due to be stationed in the oil-producing country as part of an EU security force. The EU is supporting Mr Deby, and the French - who have a bilateral arrangement in their former colony - have threatened to attack rebels if civilians are targeted.
But human rights bodies have expressed concern about the disappearance of the opposition politicians who are not connected to the rebels.
"We have no idea of their conditions of detention, we have no idea where they are. As far as we know, they have not been seen by the ICRC [International Committee of the Red Cross]," said Reed Brody, of Human Rights Watch.
Mr Brody said many Chadians, including prominent human rights campaigners, had gone into hiding since last week's arrests for fear they would be detained.