Amnesty International has launched an online petition to reveal the fate of 75,000 people who were forcibly disappeared during the war in Syria.
The Syrian government is subjecting tens of thousands of civilians, aid workers and peaceful activists to enforced disappearance or arbitrary detention – just to spread fear and collective punishment amongst the Syrian civilian population
the organisation said in a statement posted on its website.
"Many have been tortured or ill-treated in prisons, and more than 15,000 have died in custody as a result," it added.
The rights watchdog also held armed opposition groups in Syria responsible for "the enforced disappearance of hundreds of individuals in the areas they control, subjecting them to torture and other forms of ill-treatment."
The group accused the Syrian regime and armed groups of violating international law, saying the practices are carried out as part of a widespread and organised campaign against the civilian population.
It urged Russia and the United States to put pressure on the Syrian regime and armed groups to reveal the fate of the disappeared persons.
According to the Action Group for Palestinians of Syria as many as 1,688 Palestinians have been forcibly disappeared in the Syrian regime's prisons.