North Korea has been using “innovative evasion techniques” to send materials needed for chemical and ballistic weapons production to Syria over the last five years, a new report from the UN says.

The leaked study found 40 shipments of items including industrial-level amounts of acid and heat-resistant tiles and pipes, as well as ball bearings and fibre-optic cable, were sent from Pyongyang to Damascus between 2012-2017.

The 200-page report, due to be published mid-March, also alleges that North Korean ballistics specialists have visited three Syrian government weapons production plants.

Scenes of devastation in Syria after deadly shelling and airstrikes and eastern Ghouta

It has been leaked to media as rebel factions in the besieged Damascus suburb of eastern Ghouta accuse the regime of using chlorine during the fierce 12-day-old bombing campaign on the area.

The Sunday attack killed one little boy and hospitalised 18 other people who first responders said had symptoms consistent with exposure to the poison gas. Monitors confirmed the child died of suffocation but could not determine whether chlorine was present.

Bashar al Assad’s government and its Russian allies said any attack had been orchestrated by al-Qaeda linked rebels in eastern Ghouta in order to pin blame on Damascus.

Eastern Ghouta bombings: Syrian war in pictures Show all 14 1 /14 Eastern Ghouta bombings: Syrian war in pictures Eastern Ghouta bombings: Syrian war in pictures A Syrian woman and children run for cover amid the rubble of buildings. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures Smoke rises from buildings following the attack on the village of Mesraba in the rebel-held besieged Eastern Ghouta region on the outskirts of the capital Damascu. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures Injured children receive medical treatment. EPA Eastern Ghouta bombings: Syrian war in pictures A Syrian man carries a child injured. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures An injured child receives treatment following bombings on several areas of eastern Ghouta. EPA Eastern Ghouta bombings: Syrian war in pictures A child reacts inside a hospital after relatives were injured in the bombing. EPA Eastern Ghouta bombings: Syrian war in pictures Syrian children cry at a make-shift hospital in Douma following air strikes on the Syrian village of Mesraba. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures Syrian Civil Defense group extinguishing a store during airstrikes and shelling by Syrian government forces. AP Eastern Ghouta bombings: Syrian war in pictures A wounded 12-year-old Syrian boy, cries as he receives treatment at a make-shift hospital. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures Syrians carry a wounded man. AFP/Getty Eastern Ghouta bombings: Syrian war in pictures An injured man covered with blood at a medical point. Reuters Eastern Ghouta bombings: Syrian war in pictures People sit a medical point in the besieged town of Douma, Eastern Ghouta. Reuters Eastern Ghouta bombings: Syrian war in pictures Syrian Civil Defense running to help survivors. AP Eastern Ghouta bombings: Syrian war in pictures Injured children receive medical treatment. EPA

The Syrian government has been frequently accused of using chemical weapons, including chlorine and the nerve agent sarin, on civilian populations.

It agreed to give up its chemical weapons stock to international investigators after a sarin attack in eastern Ghouta in 2013 which killed hundreds of people – widely believed to be the worst chemical incident in modern history.

The UN report was compiled by a panel of experts appointed in 2016 to monitor international sanctions levied on North Korea because of its nuclear programme.

It details “substantial new evidence” about North Korea’s dealings with Syria dating back to 2008 via Ryonhap-2 and Komid, the pariah state’s main weapons companies.

The Syrian Scientific Studies and Research Centre (SSRC) – a Syrian government agency – is alleged to have paid Pyongyang for the equipment via a number of front companies.

The panel also found that North Korea had supplied weapons materials to several other countries in Africa the Middle East and Asia, including the military junta in Myanmar.

Boris Johnson suggests the UK could strike Syria in response to Assad's attack on eastern Ghouta

It said Chinese company Cheng Tong Trading Co may have sent the illegal shipments to Damascus-based companies in 2016-2017.