"This kind of conflict, this kind of a crisis always has a history ... The ISIS troops, the weapons - these are lost sons, with some of them from Iraq," Mueller told German public broadcaster ZDF.

"You have to ask who is arming, who is financing ISIS [ISIL] troops. The keyword there is Qatar - and how do we deal with these people and states politically?" said Mueller, a member of the Christian Social Union (CSU), the center-right Bavarian sister party of Angela Merkel's Christian Democrats.

Mueller did not elaborate and presented no evidence of a Qatari link to ISIL. A German government spokesman said he was checking whether Mueller's remarks reflected the official view of Berlin.

Officials at the Foreign Ministry of Qatar, a wealthy Persian Gulf Arab state, did not immediately respond to requests for comment on his accusation.

Germany's foreign and defense ministers said on Wednesday that Germany was prepared to send arms to Kurdish security forces in northern Iraq fighting ISIL and would immediately deliver military equipment such as helmets and security vests.

In March, David Cohen, the US Treasury Under Secretary for Terrorism and Financial Intelligence, cited reports of Qatari backing for Takfiri militants in Syria and described this as a “permissive jurisdiction” for donors funding the militants. 

Qatar has also strongly backed Egypt's Muslim Brotherhood, outlawed since the Egyptian military overthrew an elected president in 2013, and has given refuge to many foreign extremists including from the Taliban.

ISIL has overrun broad swathes of northern and western Iraq with little resistance. They have pushed back Kurdish regional forces allied with the Baghdad central government and driven tens of thousands of minority communities including Christians and Yazidis from their homes.

NTJ/NJF