Questions have been raised about documents that seemed to indicate that the leader of the Islamic State, Abu Bakr al-Baghdadi, was able to hide out in a hostile area of northwestern Syria because ISIS paid members of a rival jihadist group.

A n independent Syria researcher , Aymenn Jawad al-Tamimi, said he believed that the documents, which were central to an article published in The New York Times on Oct. 30, had been forged.

The documents were provided to The Times by Asaad Almohammad, a retired American intelligence operative who is now a senior research fellow at the George Washington University Program on Extremism.

They purport to be receipts for payments made by the security branch of the Islamic State to members of Hurras al Din, a Syrian jihadist group known to be an enemy of ISIS. The receipts showed that the payments were for services like security and logistical expenses.