A massive leak of top-secret Islamic State documents has exposed details of the terrorist network’s global recruitment program.

The Times newspaper published Thursday a report about the leak of classified documents from the so-called 'Islamic State of Iraq and the Levant' (ISIL) takfiri group, revealing the data of thousands of ISIL recruits, including Britons.

"Security services were last night examining files alleged to contain names, addresses and family contacts of 22,000 jihadist fighters, including at least a dozen British recruits," The Times reported.

The leak, according to the daily, was hailed as a severe setback for ISIL, providing vital intelligence on the war effort in Syria and Iraq.

The Times said that security agencies discovered that ISIL established a human resources center to make interviews with recruits and to take private information about them.

The accepted recruits can then choose whether to be suicide bombers or soldiers, or to be committed to other tasks, it added.

The leaked documents show that ISIL had recruited fighters from 50 countries, 70 percent of whom are Arabs, while most foreigners are from France, Germany and Britain.

It is believed that the man who leaked the documents was within the ranks of the so-called 'Free Syrian Army', then he joined ISIL before fleeing away.

"The group has become under the control of former soldiers of Saddam Hussein's regime, and it is no longer committed to the teachings of Islam," the daily quoted the soldier as saying.