A laptop retrieved from an ISIS hideout which contained shocking plans to develop weaponised bubonic plague that could inflict 'huge casualties' has been pictured for the first time.

The computer was recovered from an Isis hideout in Syria by a moderate rebel commander called Abu Ali.

He said that Isis fled from the building before his men stormed it. A dusty laptop was found inside, which was then handed over to a pair of investigative journalists.

The laptop found in an Isis hideout is believed to have contained a shocking document with plans to develop weaponised bubonic plague

An Isis member parades the group's flag. Plans to develop weaponised bubonic plague have been found on a laptop captured from Isis

They trawled through the computer's files and discovered a disturbing 19-page document containing instructions for making weaponised bubonic plague (biological name Yersinias pestis), including the steps needed for testing it.

'The advantage of biological weapons is that they do not cost a lot of money, while the human casualties can be huge,' the document states, according to Foreignpolicy.com.

It stated that testing should be done on small mice first.

It added: 'When the microbe is injected in small mice, the symptoms of the disease should start to appear within 24 hours.'

The laptop belonged to a Tunisian chemistry and physics student called Muhammed S, who it's thought joined the terrorist group in Syria.

However, Jennifer Cole, Senior Research Fellow, Resilience & Emergency Management, at the Royal United Services Institute, downplayed the danger the find signified.

New threat: The laptop belonged to a Tunisian chemistry and physics student called Muhammed S, who it's thought joined the terrorist group in Syria

She told MailOnline: 'This is nothing a security analyst wouldn't expect to find on a jihadist laptop. We've seen it time and time again.

'Plus, biological weapons are extremely unpredictable and their spread cannot be predicted or controlled. This is why regimes and terrorist groups have been so reluctant to use them.

'They are slow acting, can't be geographically contained and are as likely to hurt you as the enemy. That's why, while lots of groups look into them, none ever use them.'

She added that bubonic plague 'can be treated with simple antibiotics these days, so no threat anyway' and that polio in Syria is a far bigger worry than biological weapons.

Footage of another fifteen members of Kurdish militia captured by the brutal jihadists has been released

The discovery follows the release by Isis of a new decapitation video, threatening America for the second time and urging the Kurds to break from their alliance with the West against the caliphate.

It came just hours after Isis released shocking footage of the mass execution of 300 Syrian national army soldiers in the Syrian desert.

The grainy video, accompanied by the hashtag '2ndAmessagetoAmerica', shows the vicious beheading of a Kurdish soldier, who was part of a group of 15 fighters likely to have been captured by Isis during the fighting in Iraq.

The group's first warning ten days ago was entitled 'A Message to America' and showed the decapitation of American journalist James Foley.

In the latest video, the captors first issue a warning they will continue to decapitate prisoners should America continue to support the Kurds in their fight against the Islamic State.

They then behead one of the captives on a sandy roadside in Iraq, where the Great Mosque of Mosul can be seen in the background.

Kurdish forces have been in fierce fighting with Isis since June and their militias have been beginning to receive considerable amounts of armaments from Western powers including the USA and UK.