(CNN)Rights groups are calling for the release of jailed Yemeni journalist Adel al-Hasani after news of his more than five-month detention broke earlier this month.
Hasani, who has worked with several prominent media outlets including CNN, was detained at a checkpoint on the outskirts of Aden last September.
At the time of his arrest, Hasani was working to secure the release of two European journalists who were held in the port city of Mocha and later deported, according to one of those journalists who spoke to CNN on condition of anonymity due to security concerns.
The 35-year-old is being held at al-Mansoura prison by the Southern Transitional Council (STC), a secessionist group backed by the United Arab Emirates, which controls large parts of southern Yemen.
Human Rights Watch and the Committee to Protect Journalists have accused the STC of arbitrarily detaining Hasani and say he was beaten by his interrogators and subject to solitary confinement and sleep deprivation.
"More and more journalists across Yemen are subjected to threats, intimidation, violence, or detention simply for doing their jobs reporting on the country," Afrah Nasser, a researcher at Human Rights Watch said in a report published Monday.
"The Southern Transitional Council's deplorable treatment of Adel al-Hasani further stains the appalling rights record of the STC and their UAE backers."
Hasani worked with CNN on multiple assignments dating back to 2017 including an exclusive investigation that found the UAE and its coalition partners had transferred American-made weapons to al Qaeda-linked fighters, hardline Salafi militias, and other factions waging war in Yemen, in violation of their agreements with Washington. The 2019 report, which did not name Hasani due to security concerns, received two Emmy nominations.
After his arrest, Hasani was charged with conspiring with foreign agents and months later with obtaining illegal monies, his lawyer Liza Manaa Saeed told CNN.
"These are baseless allegations," Saeed said, "It is entirely normal and expected that Adel's occupation as an international journalist requires him to communicate with foreigners and handle foreign money."
Both cases were eventually dropped due to a lack of prosecutorial evidence, Saeed says, but local courts have so far refused to issue an acquittal or grant his release from jail.
"His detention is now illegal and in direct violation of the law," Saeed said. The Committee to Protect Journalists called on authorities to release Hasani immediately and stop harassing and targeting journalists.
"Adel al-Hasani's months-long detention for no discernible reason other than his work covering the ongoing conflict in Yemen is further evidence of the grave dangers faced by the press throughout the country," a statement from the organization read.
CNN recently obtained a voice note from one of Hasani's friends, purportedly recorded on February 1 by Hasani from inside his jail cell, appealing for international help.
CNN cannot independently verify the authenticity of the audio recording.