Rival militants seized the laptop during a raid on an ISIL hideout in Idlib Province close to Turkey's border.

A commander in a rival militant group in Syria has told American magazine, Foreign Policy, that the computer belonging to a Tunisian militant, contained thousands of secret files in French, English, and Arabic.

It also contained lessons on disguise, bomb-making, stealing cars as well as ideological justifications for militancy, the commander added.

Western media reports say one of the documents included instructions on how to develop biological weapons and how to weaponize the bubonic plague from infected animals.

"The advantage of biological weapons is that they do not cost a lot of money, while the human casualties can be huge," the 19-page document in Arabic stated.

The laptop also includes a 26-page fatwa (decree) by ISIL terrorist leaders on the use of weapons of mass destruction.

The Syrian government has reported of use of chemical weapons by foreign-sponsored militants three times in Syria-- once near Aleppo, a second time near Damascus, and another time in Homs in recent years.

UN investigators said in May 2013 that they had found testimonies from victims and medical staff that show militants had used the nerve agent sarin in Syria.

Senior Syrian officials say Damascus is "genuinely worried" that Syria’s enemies could provide chemical weapons to armed groups "and then claim they had been used by the Syrian government.”

The Syria crisis began in March 2011, and many people, including large numbers of soldiers and security personnel, have been killed in the violence.

ISIL terrorists have been behind many of the deadly bomb attacks targeting both civilians and government institutions across Syria over the past three years.

RA/SHI