The extracts of the study by defense consultancy IHS Jane's were published on Monday in the British Daily Telegraph.

IHS Jane's estimates that some 10,000 militants are fighting for groups affiliated with al-Qaeda such as al-Nusra Front and the rest fight for different militant groups.

The analysis also said that a large number of extremists from foreign countries are active in Syria.

Over the past few days, scores of Takfiri militants - mostly foreign mercenaries - have been killed in clashes with Syrian army soldiers in different parts of the country.

Earlier on Thursday, Saudi national Abu Turab al-Najdi who was a leader of al-Qaeda-linked group the Islamic State of Iraq and Syria was killed in Syria’s al-Regheh town in north eastern Syria.

Syria has been gripped by deadly unrest since March 2011. According to reports, the Western powers and their regional allies -- especially Qatar, Saudi Arabia, and Turkey -- are supporting the militants operating inside Syria.

According to the UN, more than 100,000 people have been killed and a total of 7.8 million of others displaced due to the violence.

People have been witnessing brutal scenes of killing and torture in some areas of the country which have been occupied and controlled by anti-Syria groups.

As the Syrian government is struggling with internal and external threats of wider conflicts, people have been forced to live under strict rules imposed by some of the militant groups who benefit international silence on their crimes.

A US plan to bomb the country over a chemical attack near Syrian capital on August 21 was canceled with Russia’s mediation that sought to ease the tensions by putting Syria’s stockpile of chemical weapons under international control.

The offer was widely welcomed both in Syria and other countries that were concerned by US military ambitions and its regional consequences.

RA/SHI