A Palestinian refugee has recently died under torture in Syria’s state run penal complexes, bringing the toll of fatal torture in Syrian prisons to over 600.

The Action Group for Palestinians of Syria (AGPS) said in a Monday report that Mamdouh Rebhi Khalifa was fatally tortured in Syrian government prisons, where he had been locked up for nearly six months.

The victim, a resident of Yarmouk refugee camp, was arrested in May 2014 at his home in Kafr Sousa, in Damascus.

On Sunday, AGPS said Palestinian refugee Mohamed Zreiq also died under torture in Syrian government prisons, where he had been locked up for over one year and a half.

The victim, a former resident of Mesyaf city, in Hama’s suburbs, had been arrested by the Syrian security forces on three occasions over his participation in peaceful protests held across Damascus.

AGPS data indicates that 618 Palestinian refugees have died under torture in Syria’s state-run penitentiaries.

AGPS estimates the real number to be far higher due to the gag orders slapped by the Syrian government on the detainees’ names and fates, along with the families’ reluctance to report such cases over retaliation concerns.

Affidavits by ex-detainees have provided evidence on the involvement of Syrian government officers in harsh torture tactics, including electric shocks, heavy beating using whips and iron sticks, and sexual abuse against Palestinian prisoners, in a flagrant violation of the Convention against Torture and Other Cruel, Inhuman or Degrading Treatment or Punishment, commonly known as the United Nations Convention against Torture (UNCAT).

The rights group urged the Syrian government to disclose the fate of scores of Palestinians held in its lock-ups, release the bodies of those tortured to death, to seriously work on halting harsh torture tactics, launch fact-finding probes into crimes of torture, and to bring those involved in such crimes before courts.