North Korea reportedly continued to enhance its nuclear and ballistic missile programs last year in breach of United Nations sanctions.

Citing a confidential U.N. report, Reuters reported on Monday that North Korea illicitly imported refined petroleum and exported some 370 million dollars worth of coal with the help of Chinese barges. 

The report to the UN Security Council North Korean sanctions committee said that North Korea exported three-point-seven million tons of coal between January and August last year, with an estimated value of 370 million dollars.

It added that most of the coal exports, an estimated two-point-eight million tons, were conducted via ship-to-ship transfers from North Korea-flagged vessels to Chinese local barges. 

The report said North Korea's annual imports of refined petroleum have been capped by the UN Security Council at 500-thousand barrels, but the country imported refined petroleum that exceeded the cap "many times over" last year. 

In addition, the UN report said that North Korea uses illicit external procurement for some components and technology, and continued to develop infrastructure and capacity for its missile program last year.