Palestinian prisoner Dirar Abu Sisi is still being held by Israeli authorities in solitary confinement since his detention began over four years ago, a prisoners’ rights groups reported.

The Palestinian Prisoners’ Society said Wednesday that Abu Sisi told his lawyer that Israeli authorities are imposing several sanctions on him, including preventing him from receiving family visits in the Nafha jail where he is currently detained.

PPS added that an Israeli court had recently sentenced Abu Sisi to 21 years of jail.

In March, a Beersheva District Court reportedly convicted Abu Sisi in a plea bargain arrangement wherein the prosecution was set to ask the court for the 21-year sentence after several initial charges were dropped.

PPS head Qadura Fares could not give further information regarding the recent sentence.

Abu Sisi, 42, was an engineer and former technical director at Gaza’s sole electricity plant. He reportedly disappeared from a train in Ukraine in February 2011, and Israel later announced he was being held by Israeli authorities.

According to a summary of charges given by Israel, Abu Sisi was on trial for “activity in a terrorist organization, hundreds of counts of attempted murder, conspiracy to commit murder and arms production offenses” as a member of Hamas.

His Israeli lawyer, Smadar Ben-Natan, said following his detention that her client had made confessions “under very heavy duress which I would characterize as torture.”

Israeli media reported at the time that Abu Sisi admitted to assisting the Hamas movement in improving its rocket capabilities.

Hamas has denied that Abu Sisi had any connection to the organization.

In order to end mass hunger strikes by prisoners held in Israeli jails in May 2012, Israeli authorities had pledged to move 19 prisoners held in long-term solitary confinement for so-called security reasons, one of whom was Abu Sisi, according to prisoner’s rights group Addameer.

While all but Abu Sisi were moved from solitary confinement during the deal, Addameer warned following the agreement that continued use of the practice shows that “Israel’s use of isolation for punitive reasons as a policy remains unchanged.”

Solitary confinement and isolation are both reportedly used in Israeli prisons.

Detainees in solitary confinement are held in an empty cell containing only a mattress and a blanket, and rely on the Israeli Prison Service to address all other needs.

Following the May 2012 deal, Abu Sisi said that “keeping me in solitary confinement is a practice of revenge by the Israeli prison service to satisfy the public in Israel.” MAANNEWS