* Rights group calls for referral to international court
* Refugees witnessed 31 methods of torture
By Adrian Croft
LONDON, March 14 (Reuters) - Syrians detained during a year-long uprising against President Bashar al-Assad's rule have been subjected to widespread torture that amounts to a crime against humanity, Amnesty International said on Wednesday.
The rights group said the situation in Syria should be referred to the prosecutor of the International Criminal Court. However, only the United Nations Security Council can do that and it is divided over the violence in Syria.
Amnesty's report, based on interviews last month with Syrians who had fled to Jordan, documents 31 methods of torture or other ill-treatment meted out by security forces, army and pro-government armed gangs, described by witnesses or victims.
"The testimony presented in this report, taken in the context of other human rights violations committed against civilians in Syria, is yet further evidence that torture and other ill-treatment in Syria form part of a widespread and systematic attack against the civilian population, carried out in an organized manner and as part of state policy and therefore amount to crimes against humanity," Amnesty said.
The United Nations says more than 8,000 people have been killed in Syria since the violence began. This is not the first time Amnesty has added its voice to growing international alarm over human rights abuses committed there.
The Syrian government says it is fighting foreign-backed "terrorists" it blames for killing hundreds of soldiers and police, and has sometimes blamed them for some of the atrocities of which it has been accused.
The former detainees interviewed by Amnesty in Jordan said they had suffered or witnessed methods of torture including beatings on all parts of the body, cigarettes stubbed out on the body, electric shocks, or being forced to watch the rape of another detainee.
Other methods included forcing a detainee into a tyre, which was then hoisted up and the person beaten; beating on the soles of the feet; and the so-called "flying carpet" where a victim is strapped face-up onto a foldable wooden board, the ends of which are moved towards each other, hurting the detainee's back at the same time as the victim is beaten, the report said.
An 18-year-old student identified only as Karim told Amnesty that his interrogators used pincers to remove flesh from his legs when he was being held at an Air Force Intelligence branch in Deraa in December 2011.
Another former detainee, named as Tareq, told Amnesty that during his interrogation at the Military Intelligence branch in Kafr Sousseh, Damascus, in July 2011 he was forced to watch the rape of another prisoner.
Amnesty said people were almost invariably beaten and otherwise tortured and ill-treated during arrest, often during transportation to detention centres, and routinely upon arrival at the detention centres and afterwards. Among the victims were children aged under 18, it said.
The torture appeared intended to punish, to intimidate, to coerce "confessions" and perhaps to send a warning to others, it added.
"In almost all cases the detainees are held in incommunicado detention, often for lengthy periods, with no access to visits from their families or lawyers in conditions which all too often amount to enforced disappearance," it added.
Amnesty said torture and other ill-treatment had been rife in Syria for decades, particularly in the 1980s and early 1990s. The situation improved somewhat after that, but in the past year violations had returned to the high 1980s' levels, it said.
While the vast majority of alleged violations had been committed by security forces, it said there had been some reports of abuses committed by members of armed opposition groups.
Independent U.N. investigators led by Paulo Pinheiro said last month that Syrian forces committed crimes against humanity including murder and torture on orders from the "highest level" of Assad's government. (Editing by Andrew Osborn)