Iraqi forces say they have uncovered a terrifying arsenal of weapons including mustard gas at an ISIS arms warehouse in Mosul.

The weapons were found among dozens of rockets hidden in a storage unit in the city with Iraqi troops claiming the haul presented a 'huge chemical threat'.

Pictures show officials examining piles of missiles which had been recklessly dumped on top of each other by fleeing jihadists.

Officials examinine piles of missiles which had been recklessly dumped on top of each other by fleeing ISIS jihadists in Mosul

Iraqi forces say they have uncovered a terrifying arsenal of weapons including mustard gas at an ISIS arms warehouse in Mosul

Outside, large rockets can be seen in open wooden crates. Separately, the Iraqi army said some rockets may have dated back to the era of former dictator Saddam Hussein.

One was found with the Russian word for 'training' on the outside - but the Iraqi army, which posted the images online, say ISIS often reconstruct such devices to use in combat.

A message accompanying the pictures states: 'Iraqi special forces find stores of Mustard Gas & dozens of large rockets in ISIS warehouses in Mosul. Huge chemical threat.

'Warehouse is full of rocket materials. Warheads, rocket bodies and training bodies too. Believed to be from rocket forces of Saddam.'

Meanwhile, the Iraqi army, buoyed by their victory this month in liberating the eastern half of Mosul from ISIS militants, is now pushing into ISIS-held villages north of the city, an Iraqi officer overseeing the operation.

The chemical weapon was found among dozens of rockets hidden in a storage unit in the city with Iraqi troops claiming the haul presented a 'huge chemical threat'

Lt. Col. Diya Lafta said troops from his 9th Division began advancing toward two villages just north of Mosul in the morning and 'after a few hours they were liberated' from IS militants.

By afternoon, the village of Shereikhan had been largely freed of IS but fighting continued in the villages beyond, according to Associated Press reporters at the scene.

Thursday's military operation forced hundreds of civilians to flee. Families escaping the clashes on foot clogged the road leading into Mosul as a cloud of smoke from an IS suicide bombing rose above the horizon.

According to one fleeing resident, who asked to only be identified by his nickname Abu Sajjad for fears for his own safety, said IS fighters still firmly control a number of other villages along Mosul's northern edge.

One weapon was found with the Russian word for 'training' on the outside - but the Iraqi army, which posted the images online, say ISIS often reconstruct such devices to use in combat

The push came after Prime Minister Haider al-Abadi earlier this week declared Mosul's eastern half to be completely free of ISIS.

Iraqi forces launched the massive operation to retake Mosul in October. A U.S.-led coalition and Iraq's own air force have been carrying out airstrikes in support of the military offensive but the troops' advance has been painstakingly slow, in part to spare the lives of civilians trapped by the fighting and also because of heavy ISIS resistance.

In a statement Tuesday, al-Abadi hailed the 'unmatched heroism of all security forces factions' and public support for the operation.

ISIS still firmly controls Mosul's west, where the next phase of the fighting is expected to be much more difficult. The U.N. estimates that some 750,000 civilians are trapped in Mosul's western sector under IS rule.

Mosul - Iraq's second-largest city and ISIS's last urban stronghold in the country - fell to ISIS in the summer of 2014, when the militant group captured large swaths of northern and western Iraq.