Islamic State's income drops significantly, analysis shows

Islamic State's income and the population under its control have both fallen by about a third, a US-based analysis firm said, describing the declining revenue as a threat to its long-term rule over its self-proclaimed caliphate.

Revenue for the ultra-hard-line Sunni Muslim group, also known as ISIS or ISIL, fell to $56 million a month in March from around $80 million a month in the middle of last year, the analysis company IHS said.

Daily oil output dropped to 21,000 barrels from 33,000 barrels over the same time frame, as production facilities suffered damage from air-strikes carried out mainly by a US-led coalition.