The International Centre for the Study of Radicalization and Political Violence (ICSR) at King's College London said in a report on Monday that the defectors have fled to Turkey while some other militants have been executed for being "spies" or "traitors."
The research organization, tracking former and current militants, said a large number of militants are still attempting to escape from the Daesh extremist group. "Many are still trapped inside Syria or Iraq - unable to escape an organization that they no longer feel any allegiance for."
The report noted that most of the defectors have gone into hiding for fear of reprisal and imprisonment.
However, nearly five dozen defectors, some of them from Australia and Western Europe and Australia, have gone public with their testimonies to speak out about their disillusionment with the terrorist group since last year, the report added.
The ICSR has also urged governments to make it easier for defectors to speak out as a deterrent to others.
The defectors mentioned in the report were permanent residents of 17 countries.
Most of the defectors have said they were disillusioned by the killing of fellow Muslims, including innocent civilians.
"The defectors' voices are strong and clear: ‘ISIL (Daesh) is not protecting Muslims. It is killing them," the research center said.
One defector, identified as Ebrahim B., from Germany, said that at least two dozen of his comrades who traveled to Syria to fight the government of President Assad have become disappointed by the reality on the ground.
The latest report comes as an influx of foreign militants into Syria has prompted warnings from several European governments in recent months. A large number of Europeans and Westerners have gone to Syria to fight against the Damascus government and fears are now growing that the militants, trained in Syria, may carry out terrorist attacks once they return home.
UN Secretary General Ban Ki-moon has said that 25,000 militants from more than 100 countries have joined terrorist groups such as Daesh and the al-Qaeda-affiliated al-Nusra Front over the past few years of conflict in the Arab country. (Source Press TV)