Raqqa, Jan 19 (IANS/AKI): Islamic State has cut its fighters' salaries by 50 percent in Syria as air strikes continue to target oil fields, supply lines and cash stores, affecting its revenue streams, The Independent reported.

"On account of the exceptional circumstances the Islamic State is facing, it has been decided to reduce the salaries that are paid to all mujahideen by half, and it is not allowed for anyone to be exempted from this decision, whatever his position," The Independent said on Monday, citing a purported IS document.

"Let it be known that work will continue to distribute provisions twice every month as usual," the document said.

The document appears to have been released by IS's treasury, the "Bayt Mal al-Muslimeen" in its Syrian stronghold of Raqqa in northern Syria.

A US-led coalition, Russia, France and Britain have all been pounding IS targets and the US claimed in November that operations against IS were already causing "significant damage" to the militant group's funding.

American officials vowed to "step up the attack" and the group's Omar oilfields were the first installations targeted by British warplanes when they began bombing Islamic State in December last year.