Rights activists claim to have the names of 18,000 missing people and are aware of another 10,000 cases, BBC reported.
According to Amnesty, enforced disappearances, through arrest, detention or abduction by the state or agents acting for the state, have been the hallmark of Al-Assad family’s rule. The state denies that the person is being held or conceals their whereabouts, placing them outside the protection of the law.
In most cases, arbitrary arrest and detention of political suspects, which in itself is a breach of international law, are followed by gross violations of their right to fair and public trial or by total denial of any trial.
Fadel Abdulghani of the Syrian Network for Human Rights estimates that 28,000 people have disappeared since the beginning of Syrian uprising, BBC reported.
According to activists quoted by the BBC, the Syrian regime was resorting to mass arrests to get rid of rebels as well as to discourage people from opposing the regime.
Alice Jay, campaign director of online activist group Avaaz which has launched a campaign to save the disappeared people of Syria says "nobody is safe" from a deliberate government campaign of terror.
Syrians are being "plucked off the street by security forces and paramilitaries and being 'disappeared' into torture cells,” she told BBC.
"The panic of not knowing whether your husband or child is alive breeds such fear that it silences dissent," she said.
"The fate of each and every one of these people must be investigated and the perpetrators punished."
Avaaz has gathered testimony from Syrians who says husbands, sons and daughters have been forcibly abducted by pro-government forces.
A report published by Amnesty in March, coinciding with the first anniversary of the start of the Syrian uprising, said the scale of torture and other ill-treatment in Syria had risen to a level not witnessed for years and was reminiscent of the dark era of the 1970s and 1980s.
The document, titled “I Wanted to Die: Syria's Torture Survivors Speak Out,” said the torture and ill-treatment of insurgents caught up in the massive wave of arrests over the last year generally followed a set pattern of dehumanizing treatments.
Beating began on arrest, followed by more severe battery — including with sticks, rifle butts, whips and fists, braided cables — on arrival at detention centers, a practice sometimes called the haflet al-istiqbal or reception. Newly-held detainees were usually stripped to their underpants and were sometimes left for up to 24 hours outside, the victims said.
According to the testimonies given to Amnesty, the detainees are at most risk when being interrogated. Former detainees described three methods: dousing the victim or cell floor with water, then electro-shocking the victim through the water; the electric chair, where electrodes are connected to parts of the body and the use of electric prods.
Gender-based violence and sexual crimes against men and women have become more common ever since the revolution began last year, the report said.
According to the U.N. estimates, more than 18,000 people have been killed so far in the civil war with 170,000 seeking refuge outside Syria and 2.5 million in need of aid within the country. But according to the Syrian Observatory for Human Rights monitoring group, the violence has killed at least 33,000 people, most of them civilians. Some 1,000 people were killed last week alone, the Britain-based watchdog said Saturday.