UPDATE: Saturday 10.45pm. Riaz has been freed and is at home. He thanks everyone for their solidarity.
Dr Riaz Ahmed, assistant professor in the applied chemistry department at Pakistan's Karachi University, and elected representative on the university council, disappeared from the university at 10pm on Friday 11 May.
Having recently received threats from paramilitary forces, it is certain that he is being held by them.
A human rights defender and renowned Marxist intellectual, Dr Riaz has been a strong, non-violent voice calling for freedom of expression, for example calling for the release of missing persons such as Wahid Baloch, held for five months.
Riaz was arrested in April 2017 as he was about to address a press conference calling for the release from prison of a former colleague. Riaz was set free after seven days following a well-publicised campaign for his release.
Activists are now calling again on all progressive organisations to take notice of the illegal detention of Dr Riaz Ahmed and help ensure his immediate release.