An ISIS flag on a building in Kobane
An ISIS flag on a building in KobaneReuters

Isis militants have reportedly resorted to setting crude oil on fire in order to create a smoke cloud and disrupt US-led coalition fighter planes from making sorties against them in Syria.

According to the Syrian Observatory for Human Rights, the Islamic State militants burned crude oil on the outskirts of the al-Bahra Khatuniyyah area near the al-Hool region in Syria's Hasakah province. 

The human rights body, which has been monitoring Isis atrocities in Syria, said Isis wanted to create clouds of smoke as a screen to confuse fighter planes and lead them to miss their targets. 

The Islamic State has come to control several oil fields in Iraq and Syria since declaring their Caliphate last year, which have become one of their main sources of revenue. 

US-led coalition forces have been conducting airstrikes against Isis targets in Syria since last December, while Russian forces began airstrikes in the region on 30 September.

US airstrikes in Syria have reportedly dropped after the Russian intervention, numbering only 117 last month, the lowest in the last six months, according to reports.