The organisation has called on international organisations to take serious action to release the journalist.
Mehdi Ansari disappeared in October this year after leaving his office in the Pul-e-Surkh area of Kabul.
However, the Afghanistan Journalists Support Organisation said in a statement on Wednesday, January 8, that "the arrest of Mehdi Ansari and the charges against him on the basis of anti-government propaganda are illegal and contrary to the principles of freedom of expression".
According to a letter provided to the media, it was reported that the Taliban had issued a prison sentence for Mehdi Ansari on charges of "anti-government propaganda".
The organisation has emphasised that the arrest of Mehdi Ansari and similar actions pose a serious threat to freedom of expression and is a warning to the Afghan media community.
With the group regaining control of Afghanistan, the activities of journalists and media inside the country have been severely restricted.