*** EDIT CONTAINS GRAPHIC CONTENT ***<br/> <br />Amateur videos posted online purport to show Islamic State militants and Syrian regime forces battling for control of a military air base around Deir al-Zor province.<br/> <br />It's one of the last strongholds in the east for Syrian President Bashar al-Assad's government.<br/> <br />Islamic State controls all but a few pockets in the province, whose oilfields have been a major source of revenue for the group.<br/> <br />But its operations have come under strain in recent months...<br/> <br />...ever since a U.S.-led coalition came into the mix and started launching air strikes against them.<br/> <br />The latest battle between Islamic State and Syrian forces comes as a mass grave was revealed in Deir al-Zor province.<br/> <br />The Syrian Observatory for Human Rights says it contains the bodies of more than 230 people killed by Islamic State.
