The video is titled 'From Who Excused [sic] To Those Not Excused' - suggesting that disability is no excuse for not serving for ISIS.

In the five minute clip the two men, who are deaf-mutes and brothers, are shown working as traffic police in Iraq's second city Mosul, which has been under ISIS control since last summer.

Speaking in sign language with English and Arabic subtitles, one of the men says: 'I am a deaf mute who works in the traffic police in the Islamic State with my brother Abu Abdur-Rahman.

'As for my message to the apostate peshmerga (Kurdish fighters) we will strike you soon, by Allah's permission. I am living in a land in which Allah's sharia is established.' 

Wearing black jumpsuits, ammunition pouches and carrying what appear to be M16 assault rifles, the pair also speak about their desire to 'slaughter' their enemies including Britain, America, France and Italy, saying 'you will not stop our advance'.

The fighters also threaten Saudi Arabia, Kuwait, Qatar and those who have allied with the West, vowing to destroy them.

In the final section of the slickly produced and professionally edited film, the brothers are shown assembling simple rocket launchers which they claim are used to fire at Kurdish fighters.

The weapons consist of little more than crudely made explosives balanced on a metal frame which is tilted upwards and held in place using a few rocks.

In the last seconds of the film, which features the Islamic State's logo in the top right hand corner, one of the men presses a trigger, launching the rockets.

(dailymail.co.uk)