The US army has lost track of more than A$1.3 billion worth of arms and equipment sent to Kuwait and Iraq, Amnesty International claims, raising fears the weapons could have fallen into the hands of ISIS.

The human rights group said the figures came from a 2016 US government audit, obtained through a Freedom of Information request.

“This audit provides a worrying insight into the US Army’s flawed — and potentially dangerous system for controlling millions of dollars’ worth of arms transfers to a hugely volatile region,” Patrick Wilcken, Amnesty’s researcher on international arms control, said in a statement.

In 2015, the US gave A$2.1 billion worth of equipment to Iraq to help them fight ISIS through the Iraq Train and Equip Fund.

But the Army’s 1st Theater Sustainment Command “did not have accurate, up-to-date records on the quantity and location of [Iraq Train and Equip Fund] equipment on hand in Kuwait and Iraq,” the Pentagon’s inspector general wrote in the audit, US political news website The Hill reports.

Tens of thousands of assault rifles, hundreds of mortar rounds and armoured Humvees were among the equipment misplaced, Amnesty said.

According to Amnesty, the US army’s lack of control over its weapons was also exposed in a 2015 audit.

The 2015 audit prompted Congress to commit to keeping a stricter control of its weapons.

“This should be an urgent wake-up call for the US, and all countries supplying arms to Iraq, to urgently shore up checks and controls,” said Mr Wilcken.

In a statement, the Pentagon admitted more could be done decrease inefficiencies.