A combination of successful airstrikes by Western governments and drop in the oil price are helping to cut off a much-needed revenue stream for the so-called Islamic State (ISIS) terrorist group, an energy analyst says.
"The damage is being done, which is why we have seen ISIS oil production go from 110,000 barrels a day to 40,000 barrels a day," Amrita Sen, chief oil analyst at Energy Aspects, told CNBC Thursday.
Following Friday's terrorist attacks in Paris and confirmation that a bomb brought down a Russian airliner in the Sinai desert a couple of weeks ago -- attacks both pinned on ISIS -- the U.S., France and Russia have stepped up airstrikes on the militant group's positions in Iraq and Syria.
The key targets for airstrikes have been ISIS' main sources of revenue and operations, including oilfields, trucks used to transport oil, munitions depots, command centers and trade routes (used mainly to transport arms and oil). Earlier this week, the U.S. said it had destroyed over 100 fuel trucks in an airstrike.