Abu Sisi
Abu SisiIsrael news photo: Flash 90

An Israeli court sentenced a Palestinian engineer from Gaza to 21 years in jail Tuesday for helping the Islamist terrorist movement Hamas to improve the range of rockets used against the Jewish state.  

Dirar Abu Sisi went missing in Ukraine in February 2011, and Israel said a month later that he was in its custody and would be put on trial. He was apparently arrested in an operation by Israeli secret service agents.

A court in the southern city of Beersheba had convicted Abu Sisi of several "crimes against the security of the state."

In particular, he was said to have helped improve the range of the domestically-made Qassam rockets that Hamas's "military wing," the Ezzedine Al-Qassam Brigades - has repeatedly fired at Israeli civilians from the Gaza Strip over the years.

The rockets, produced in clandestine workshops that are often targeted by Israeli air strikes, can travel between 10 and 20 kilometers (six and 12 miles). They posses a relatively small warhead but are usually packed with shrapnel including ball-bearings, razor blades, nails and glass, allowing them to seriously maim or kill victims beyond the immediate site of impact.

Images of pock-marked walls became iconic of southern Israeli communities' struggle against relentless rocket attacks by Hamas and other terrorist organizations based in Gaza.

Abu Sisi, the former deputy engineer for Gaza's electrical plant, was indicted in April 2011 for "membership in a terror organization, conspiracy to commit a crime, the production of illegal weaponry, and assistance to an illegal organization."

According to the indictment, after Operation Cast Lead in 2009, Abu Sisi was appointed by two of Hamas's most senior commanders  to establish a military academy for hostile activity against the Jewish state. 

He was reportedly hand-picked by none other than Al Qassam Brigades elusive leader Muhammad Deif, aand his second-in-command Ahmed Jabari, who was killed in an Israeli air strike in 2012.

Abu Sisi is also alleged, according to the indictment, to have served as the commander of the military academy. 

In addition to his connections to the military academy, Abu Sisi was also a senior partner in the production of both missiles and mortars, as well increasing the range of rockets launched by Hamas into Israel. 

According to the indictment, Abu Sisi was the central developer of the Qassam rocket, among other rockets and anti-tank missiles. 

AFP contributed to this report.