The Islamic State's leadership in Syria and Iraq has been decimated by months of sustained air strikes, leaving the terror group in chaos and isolating leader Abu Bakr al-Baghdadi, it is claimed.

Allied airstrikes, including those carried out by British warplanes, have killed more than 6,000 fighters since September, including more than half the militants serving on ISIS' ruling council.

Among the dead jihadis is Abu Muslim al-Turkmani, a former Iraqi army lieutenant colonel considered Baghdadi's number two and ISIS' most senior militant in Iraq.

His death and that of as many as nine others on ISIS' 18-man leadership council have forced Baghdadi to promote local warlords to the status of regional commanders, as his inner circle of trusted advisers and battle-hardened loyalists becomes increasingly small.

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Pressure: The Islamic State's leadership in Syria and Iraq has been decimated by months of sustained air strikes, leaving the terror group in chaos and isolating leader Abu Bakr al-Baghdadi (pictured)

Dead: Among the dead jihadis is Abu Muslim al-Turkmani (left), a former Iraqi army lieutenant colonel considered Baghdadi's number two and ISIS' most senior militant in Iraq. Another former member of Saddam Hussein's army turned ISIS commander, Abu Musa al-Alwani (right), has also been killed

Terror: ISIS' leadership has been left in chaos following the deaths of many of its senior commanders

Baghdadi has not been seen in public since July and there have been numerous unconfirmed reports that he suffered serious injury or possibly even death as a result of targeted airstrikes.

The likelihood, however, is that Baghdadi has been forced deep into hiding to avoid being targeted by jets that have destroyed more than 1,000 vehicles used by terrorists over the past five months.

Other senior figures within the terror group have not been afforded that luxury and still need to travel across the vast swathes of Syria and Iraq that remain under ISIS' control.

This forces them to make a decision whether to move as part of a large military convoy and risk being spotted by warplanes overhead, or whether to use cars that reduce the likelihood of aerial detection but leave them at risk of kidnap or killing at the hands if ISIS' rivals on the ground.

Targeted: Abu Abdulrahman al-Bilawi (left) - who had been the head of Baghdadi's four man military council - was killed by a coalition warplane last year. Another militant reportedly killed in an airstrike was Abu Hajar Al-Sufi (right) who had been one of Baghdadi's most trusted advisers on the Shura Council

Despite the serious damage done to ISIS' leadership by the airstrikes, scores of prominent militants remain alive, including the terror group's British executioner in chief, Jihadi John

Among the ISIS leadership figures killed in airstrikes in recent months is Abu Musa al-Alwani, according to the Sun. Another former member of Saddam Hussein's army, Abu Musa - real name Waleed Jassem al-Alwani - had been a prominent member of ISIS' military council before his death.

Also killed by coalition airstrikes last year was Abu Abdulrahman al-Bilawi - who had been the head of Baghdadi's four man military council, having previously served on the terror leader's religious and strategic advisory body, known as the Shura Council.

Another militant reportedly killed by the first wave of coalition airstrikes in September was Abu Hajar Al-Sufi, also known as Abu Hajar al-Assafi, who had been one of Baghdadi's most trusted advisers on the Shura Council.

His death came two months before that of Abu Jurnas. real name Rathwan Talib Hussein Ismail al-Hamdani, whose official title was believed to have been Governor of 'Border Provinces'.

Abu Jurnas' role was to ensure ISIS' barbaric interpretation of Sharia law was enforced along the Syria-Iraq crossing, and to ensure that the nations' respective armies are unable to reestablish the border that was effectively wiped out by the terror group's lightning advance last summer.

Other well-known militants still alive and operational include Abu Wahib, the terror group's 28-year-old leader in Iraq's Anbar province (right), Abu Omar al-Shishani, another 28-year-old, who is understood to be responsible for ISIS' military operations within Syria

Abu Wahib's distinctive thick black beard has ensured he has been used prominently in ISIS propaganda

While many local tribal leaders are in favour of a Sunni Muslim caliphate, their allegiances remain largely tribal and they are not seen as entrenched supporters of ISIS (pictured)

Baghdadi is likely to have replaced Abu Jurnas with another of his trusted lieutenants, but in less strategically important regions he is understood to have been forced to appoint local warlords to the role of senior commander as his inner circle of loyalists dwindles.

While many of these local tribal leaders are in favour of a Sunni Muslim caliphate and their opposition to the Syrian and Iraqi regimes confirmed, their allegiances remain largely tribal and they are not seen as entrenched supporters of the Baghdadi-led group.

Long-standing tensions between the tribes has also surfaced as they battle for regional prominence and advantage, causing chaos with ISIS ranks.

Despite the serious damage done to ISIS' leadership by the airstrikes, scores of prominent militants remain alive, including the terror group's British executioner in chief, Jihadi John.

Although he is unlikely to hold a senior position within the group's leadership, his death would be highly symbolic in the battle to defeat ISIS due to his in the deaths of British, American and Japanese aid workers and journalists.

Over the weekend ISIS' British executioner in chief, Jihadi John, savagely murdered Japanese journalist Kenji Goto in a shocking filmed beheading after days of intensive negotiations through intermediaries to save him

Mr Goto joined a list of other victims, including fellow Japanese national Haruna Yukawa (left). British aid workers David Haines (centre), and Alan Henning (right) have also been murdered

US journalist James Foley (left) was the first to appear alongside Jihadi John in one of the sickening videos, followed by Steven Sotloff (centre. Aid worker Peter Kassig (right) is also dead

Other well-known militants still alive and operational include Abu Wahib, the terror group's 28-year-old leader in Iraq's Anbar province, whose distinctive thick black beard has ensured he has been used prominently in ISIS propaganda.

Another is Abu Omar al-Shishani, another 28-year-old, who is understood to be responsible for ISIS' military operations within Syria.

Before joining ISIS Georgian-born Shishani led the terror group Jaish al-Muhajireen wal Ansar in operations against the Syrian regime, but declared his allegiance to Baghdadi last year.