The jihadist Islamic State of Iraq and the Levant (ISIL) is reportedly now in full control all of main oil and gas fields in Syria, which are located in the Deir Ezzor province next to Iraq.

News24 quoted the Syrian Observatory for Human Rights monitoring group, as saying that ISIL had taken control of the Tanak oil field, located in the Sheiytat desert area in the east of Deir Ezzor province.

Earlier,the Al-Omar oil field had been seized, they added.

The tiny Al-Ward oil field is yet to be captured,but is in the hands of a local tribe.

ISIL has also reportedly taken over nearly all of the countryside, and its forces have been bolstered by heavy weapons captured from Iraqi troops fleeing an offensive that it spearheaded.

On Sunday, ISIL declared a "caliphate", referring to an Islamic system of rule that was abolished nearly 100 years ago, in a move that rebels, including Islamists in Syria, branded a "heresy".