Isis is developing its own arsenal of military grade weapons and ammunition including rockets, mortar rounds and bombs – as it battles to defend territory across Syria and Iraq, a report has found.

Facilities abandoned following the recent Mosul offensive have revealed manufacturing on “an industrial scale”, making tens of thousands of units in a tightly controlled and bureaucratic process.

Inspectors from UK-based Conflict Armament Research (CAR) gathered evidence while embedded with Iraq forces advancing on Isis’s last major stronghold in the country, finding a multitude of factories, workshops and warehouses in eastern Mosul.

James Bevan, the executive director of CAR, said its findings demonstrate Isis’s “capacity to produce weapons on a massive scale”.

“This is a centrally managed industrial programme, which produces munitions running into the tens of thousands, and taps into Turkey’s domestic markets for raw materials,” he added.

“Its impact is clearly observable on the battlefield, where Iraqi forces face near-continuous mortar and rocket fire in the battle to retake Mosul.”

In pictures: Isis' weapons factories Show all 11 1 /11 In pictures: Isis' weapons factories In pictures: Isis' weapons factories A mortar round fin manufactured by Isis in Gogjali, Mosul, November 2016 Conflict Armament Research In pictures: Isis' weapons factories Isis rocket components discovered in Gogjali, Mosul, Iraq in November 2016 Conflict Armament Research In pictures: Isis' weapons factories Isis mortars discovered near Karamlais, Iraq, in November 2016 CAR In pictures: Isis' weapons factories An Isis rocket launch frame in Qaraqosh, November 2016 Conflict Armament Research In pictures: Isis' weapons factories A memo from Isis' COSQC on quality control at a manufacturing facility in Gogjali, Mosul, November 2016 Conflict Armament Research In pictures: Isis' weapons factories Electrically-operated initiators manufactured by Isis in forces Gogjali, Mosul, November 2016 Conflict Armament Research In pictures: Isis' weapons factories Isis mortar tubes at a manufacturing facility in Karamlais, November 2016 Conflict Armament Research In pictures: Isis' weapons factories An Isis mortar production facility discovered in Gogjali, Mosul, in November 2016 Conflict Armament Research In pictures: Isis' weapons factories An Isis weapons manufacturing facilities near Mosul in November 2016 Conflict Armament Research In pictures: Isis' weapons factories Stocks of French-manufactured Sorbitol, Latvian potassium nitrate and Lebanese sugar at an Isis weapons factory in Iraq Conflict Armament Research In pictures: Isis' weapons factories A destroyed Isis weapons facility in Qaraqosh, Iraq, November 2016 Conflict Armament Research

Isis has set up an authority called the Central Organisation for Standardisation and Quality Control, which issues specific guidelines on weapon production parameters and controls manufacturing quality, the report said.

It enforces standards similar to those of national armies to ensure the weapons work and operates specialised plants for separate stages of production.

CAR investigators documented more than 5,000 rockets and mortar rounds in various stages of production, and more than 500 finished mortar rounds that had been recovered by Iraqi troops.

Labels affixed to the weapons indicated they had only been manufactured a month before being confiscated, when the multi-national advance on Mosul had started.

Most of the items used to create the weapons and ammunition are from the Turkish domestic market, CAR said, with many chemicals for explosives procured in bulk from the same factories and distributors.

Isis 'teaching children how to kill and make bombs'

The group, which previously revealed Isis was building weaponised drones, concluded that the rigorous process was not confined to the Mosul area and had been documented elsewhere in Iraq, including in Isis’s former stronghold of Fallujah.

Extremists were driven out of that city and are now resisting the advance on Mosul by Iraqi troops, backed by the US-led coalition, while fighting to hold regained territory in Palmyra in Syria.

CAR found weapons and ammunition production “on an unprecedented scale” was critical to Isis’s defence of the city.