A Syrian teenager, whose mutilated body was discovered by chance by her family in a morgue while there to identify her brother's corpse, was thought to be the first female to die in custody during recent unrest, a rights group said on Friday.
Zainab al-Hosni, 18, from the city of Homs had been decapitated, her arms cut off and skin removed, Amnesty International said.
She was abducted by men suspected of belonging to the security forces in July in an apparent attempt to put pressure on her activist brother Mohammad Deeb al-Hosni to turn himself in, the group said.
Both died, bringing Amnesty's number of reported deaths in custody to 103 cases since mass protests in Syria began in March this year against President Bashar al-Assad's rule.
"If it is confirmed that Zainab was in custody when she died, this would be one of the most disturbing cases of a death in detention we have seen so far," Philip Luther, Amnesty's deputy director for the Middle East and North Africa, said in a statement.
Fifteen new deaths in custody cases have been recorded by Amnesty since late August, with the bodies bearing signs of beating, shooting and stabbing, but Zainab's case was "particularly shocking", Luther said.
Mohammad, 27, had been organising protests in Homs, which has been at the centre of opposition demonstrations calling for political reform.
Assad, a member of the minority Alawite sect has ruled the mainly Sunni Muslim country since succeeding his late father Hafez al-Assad 11 years ago.
Mohammad's mother was summoned by security forces this month to pick up his dead body from a military hospital three days after his arrest.
His body showed signs of torture including bruising on the back and cigarette burns on the body. He had been shot in the right arm, right leg, and three times in the chest, Amnesty said.
His mother unexpectedly discovered Zainab's mutilated body at the same hospital.
She was said to have been made to sign a document saying that Zainab and Mohammad had been kidnapped and killed by an armed gang, the group added.
"There are no signs of torture and murder abating in Syria," Luther said.
The United Nations said 2,700 people had been killed in the unrest, while authorities say 700 police and army have been killed by terrorists and mutineers.
Assad has promised reform and has changed some laws, but the opposition said they made no difference.
The president has repeatedly said foreign powers were trying to divide Syria under the guise of wanting democracy due to Damascus' backing for Arab resistance groups