At least 2,100 people died in Syrian prisons last year and the bodies of many showed signs of torture, a monitoring group said on Friday, quoting the families of deceased detainees.
The British-based Syrian Observatory for Human Rights said it believed the true figure to be much higher but had only reported cases where families had received a corpse or a death certificate from a prison.
“The prisons tell the families that the prisoners died of natural causes, such as a heart attack,” Observatory head Rami Abdulrahman told Reuters.
Syrian officials could not immediately be reached for comment.
U.N. investigators said in March there were suspected war criminals in Syrian military units and security agencies as well as in the insurgent groups fighting them in the country’s civil war.
They said they were investigating evidence of torture, killing and starvation in Syrian prisons and that the heads of intelligence branches and detention facilities were on a list of potential suspects.
More than 76,000 people were killed in the war in 2014, the Observatory said, and the U.N. says 200,000 have died since the conflict started.
In January 2014, former war crimes prosecutors commissioned by Qatar said they had “clear evidence” showing the systematic torture and killing of 11,000 detainees in Syrian jails from a trove of photos supplied by a Syrian military police photographer.
The Syrian conflict began in March 2011 with popular protests against President Bashar al-Assad and spiralled into civil war after a crackdown by security forces.