Iraqi special forces say Islamic State were planning to launch long and short-range missiles tipped with chemical or biological war heads from western Mosul.

It follows analysis of material taken by French special forces working with Iraqi units in the city.

Sky News was taken to a warehouse and unloading area near the Tigris River, where dozens of missiles were stored alongside makeshift launchers.

The weapons, with Russian markings, are thought to have come from Syria. Most were designed to be fired by jets but one, a 10ft-long missile, is a type of Scud.

Even fired from a makeshift launcher, it could carry its lethal payload tens of kilometres, according to military advisers.


Image: Some of the weapons had Russian markings

Beneath the cover of trees Islamic State fighters had been working on the Scud.

The area smelt strongly of chemicals and we were warned not to touch anything.

The French soldiers advised the Iraqi team that the whole area was contaminated. Tests are now being carried out on what senior commanders called "poison".

Near the preparation site three large refrigerated cargo carriers had been opened. They are all full of coking coal but, buried inside, Iraqi soldiers found containers with the unidentified substance inside.

On the front line in Mosul

They believe the substance had to be kept at or below freezing point.

Brigadier Ali of the Counter Terrorism Service, in charge of the weapons discovery, told me he believed the production of the chemical weapons had been halted by the start of the offensive on Mosul and the targeting of IS fighters by coalition planes and drones.

"Daesh (IS) wanted to use these weapons and had spent a long time modifying," he said.

Allegations of chemical weapons use, particularly chlorine, in the Syrian conflict have been levelled at all sides. But the discovery of a substance perhaps even more lethal than chlorine is a new and frightening development.

A year ago Sky News revealed the existence of a "jihadi university" in the Syrian IS stronghold of Raqqa, where a training programme for modifying missiles and IEDs was well established.

Image: A container holding an unidentified substance that senior commanders are calling 'poison'

The weapons we witnessed in Mosul are very similar to those being worked on in the video passed to Sky News by members of the Free Syrian Army, who arrested an IS operative making his way to Europe with the videos.

The weapons discovery comes as the commander leading the attack on Mosul called on President Donald Trump to continue to support the operation and guarantee the involvement of US warplanes in the offensive.

General Abdul Wahab Al Saadi balked at the new President's description of the operation as a "disaster".

"We are on the ground, not the President," he told me on the outskirts of Mosul.

Sky News looks inside an Islamic State prison

"I took one month to take Fallujah, without American air support it would have been six months and would cost me a lot of men. It would be the same in Mosul but this is a different battle and would be worse."

The Iraqi Special Forces are now in full control of eastern Mosul and preparations are under way to launch an offensive on the west of the city.

The Tigris river divides Iraq's second largest city into two.

Islamic State forces are readying themselves for the final showdown with Iraq's military.