The report, which was submitted to the UN Security Council said the North "continued to export nearly all the commodities prohibited in the resolutions. between January and September 2017".
It said shipments of coal had been delivered to China, Malaysia, South Korea, Russia and Vietnam in breach of sanctions using "a combination of multiple evasion techniques, routes and deceptive tactics".
Pyongyang has also reportedly been supplying weapons to war-stricken Syria and Myanmar.
The UN monitors also said one country, which they did not identify, reported it had evidence that Myanmar received ballistic missile systems from North Korea, along with conventional weapons, including multiple rocket launchers and surface-to-air missiles.
The U.N. and United States have introduced a wave of sanctions aimed at curbing North Korea's development of nuclear weapons, including by seeking to reduce its access to crude oil and refined petroleum products.
This undated photo released by North Korea's official Korean Central News Agency (KCNA) on February 1, 2018, shows North Korean leader Kim Jong-Un at the newly-remodeled Pyongyang Trolley Bus Factory in Pyongyang.
United Nations monitors also said North Korea had flouted UN financial sanctions through "deceptive practices" and engaged in "widespread conventional arms deals and cyber operations to steal military secrets". Papers showed Russian Federation and China as the origin countries, instead of North Korea.
The UN monitors investigated 16 coal shipments between January and August 5 to ports in Russia, China, Malaysia and Vietnam.
North Korea's economy has been heavily reliant on Beijing-$2.3 million of the $2.83 billion total exports were shipped to China in 2015.
"Technicians continue to operate at chemical weapons and missile facilities at Barzei, Adra and Hama", a member-state, which was not named, told the panel.
Syria denied co-operation with North Korea on their chemical weapons programmes, saying that the only experts it was hosting from the country were involved in sports.
News of the report came hours after US Secretary of Defence Jim Mattis said that the US was investigating the Syrian government over reports that it was using the deadly nerve gas sarin on the battlefield.
"We must put an end to illicit ship-to-ship transfers that undermine United Nations sanctions", he said.
Investigators looked at 40 previously unreported North Korean shipments between 2012 and 2017 to Syria's Scientific Studies and Research Centre, a body which oversees the country's chemical weapons program.