In the war-ravaged town of Mosul, a teddy bear or truck is a rare treasure to a child.

But these innocent-looking toys are actually the trigger for sinister booby traps that detonate as soon as they are touched.

The ploy marks a sickening new low for Islamic State, who currently hold Iraq’s second largest city, as they can only be intended to target children. Adults would walk straight past them.

These and other cunningly disguised improvised explosive devices (IEDs) have been put on display at a training centre for locally-trained bomb disposal experts as 40,000 soldiers, state-sanctioned militia members and other fighters prepare to encircle Mosul to cut off IS forces from outside help.

Disguise: This seemingly harmless toy truck is actually a trigger for an explosive device

Sickening: An innocent-looking teddy bear is actually a bomb meant for Iraqi children

Colonel Nawzad Kamil Hassan, an engineer with the Kurdish forces, told the Observer: ‘Why would Isis use something nice, like a bear or a rabbit?

‘They used this toy because they know the peshmerga [Kurdish fighters] will not touch it but children will.’

He added: ‘They are not even animals. They are worse than animals.’

His unit has cleared 50 tonnes of explosives in two years from areas once controlled by militants, including five tonnes from a single school in Sinjar city to the west of Mosul.

The city, around 250 miles north of Baghdad, has been under IS control since June 2014.

The offensive to take it back is the largest deployment of Iraqi forces since the 2003 invasion by the U.S. and coalition forces.

The U.S. military estimates IS has up to 5,000 fighters inside Mosul and between 1,500 and 2,500 in a defensive belt around the city.

Of these, around 1,000 are believed to be foreign fighters.

Other IEDs, including some with detonators attached to playing cards, watches and lengths of hosepipe, have been laid out to slow the encroaching forces and delay recovery should they succeed in seizing control.

A spokesman for Popular Mobilisation Units, an umbrella group for the militias, yesterday confirmed around 15,000 Shiite fighters would be participating in the offensive.

ISIS fighters behind the bombs have been described as 'worse than animals' (file picture)

The involvement of Iranian-backed Shiites has raised concerns about sectarian tensions becoming inflamed in the mainly Sunni city.

The militias have been accused of committing abuses against citizens in other Sunni areas taken back from IS.

Turkey’s president warned their behaviour would be closely monitored to safeguard ethnic Turkmens in Iraq.

Recep Tayyip Erdogan said a Turkish response could be triggered if militias ‘terrorise’ the Iraqi-Turkmen town of Tel Afar during the push around Mosul.