Reporters Without Borders is very concerned about Jean Etienne Laokolé, an opposition blogger who has been held by the Chadian security forces for the past three weeks, and calls for his immediate and unconditional release.
Laokolé, who was arrested in N'Djamena on the night of 22 March, is also an author, activist and humanitarian worker.
"Protests in Chad and abroad - by organizations such as Internet Without Borders, Human Rights Without Borders and Amnesty International - failed to elicit any information from the authorities about Laokolé and why he is being held," Reporters Without Borders said.
"What is he supposed to have done, why has he been held for such a long time, and why is he being held incommunicado? Everything indicates that the authorities did not like what he was posting online under the blog name of Vourboubé Pierre, and that they arrested him when it was revealed that he was the blogger."
Reporters Without Borders added: "We urge the Chadian government to immediately provide information about the state of Laokolé's health and the reasons for his detention."
On the night of 22 March, Laokolé was driving with family members in the N'Djamena district of Atrone when he was stopped by a group of men in civilan dress and was forced to get into their vehicle.
Amnesty International has quoted Chadian human rights activists as saying he was seen three days later in the former OCAM military camp and was subsequently transferred to an unofficial camp at Amsinene, 30 km outside the capital, which is notorious for its use by the intelligence services for heavy-handed interrogation and torture.
According to his family, Laokolé had been summoned for questioning by the criminal investigation police earlier on the day of his arrest as the result of a complaint about an article posted on an exile blog called Le blog de Makaila (http://makaila.over-blog.com/) under the pseudonym of Vourboubé Pierre.
The plaintiffs claimed that the blog post made "false accusations" against them. After negotiations, Laokolé gave them an apology. But the complaint served to confirm that he was the writer who used this well-known blog name.
Three days before his arrest, he was named as the blog's author in an article on the pro-government blog VisionduTchad.net that began: "Who is this author? Our blog has discovered who is hiding behind these pseudonyms and who is flooding us with disinformation." It named not only Laokolé but also members of his family and gave details about his personal life.
His last blog entry, posted on 16 March, may also have prompted his arrest. It identified a number of persons as working as intelligence agents for Jean-Bernard Padre, the minister of land affairs.
Laokolé is the son of Jean-Baptiste Laokolé, the deputy general secretary of the opposition Freedoms and Development Party (PLD), and nephew of Saleh Kebzabo, a parliamentarian and president of the opposition National Union for Development and Renewal (UNDR).