Weapons exported by the UK during the Iraqi invasion may have ended up in the hands of Islamic State (Isis) militants in Iraq and Syria, a rights group report says. Amnesty International's latest finding warns that hundreds of thousands of assault weapons channelled by the US-led coalition in the wake of Iraq War in 2003 had gone astray, potentially filling up the current arsenal of IS (Daesh).

The 44-page report titled Taking Stock: The Arming of Islamic State, released by the human rights organisation, was based on the expert analysis of thousands of images of the extremist group, which is trying to establish a caliphate in the conflict-ridden region.

Most of the weapons from Daesh's arsenal were from the armouries of the Iraqi army, which the militants obtained by force. Almost all of those arms were supplied by various nations when they were engaged in a bloody war between 2003 and 2007.

The report said: "The UK was also involved in supplying the Iraqi security forces. In early 2007, China shipped approximately 20,000 assault weapons to the UK for onward shipment to the Iraqi security forces. Similarly, between March 2005 and December 2006, a variety of small arms and light weapons were exported from Bosnia and Herzegovina and Serbia to the UK, and then re-exported to Iraq."

The report blames poor regulations over arms trading in the region as the key cause of Western weapons ending up in the hands of terrorists. "The vast and varied weaponry being used by the armed group calling itself Islamic State is a textbook case of how reckless arms trading fuels atrocities on a massive scale," said Patrick Wilcken, Researcher on Arms Control, Security Trade and Human Rights at Amnesty.

"Poor regulation and lack of oversight of the immense arms flows into Iraq going back decades have given IS and other armed groups a bonanza of unprecedented access to firepower," he added. The vast array of internationally-manufactured weapons acquired by the extremist group have allowed them to seize more territories and strengthen their foothold in Iraq and Syria. The successive governments' inabilities to wield a complete control over the military stockpiles also compounded the problem.