Beijing was forced to defend its trade with North Korea on Tuesday after it emerged that Chinese-made trucks were used to display missiles in a huge military parade that was staged by Pyongyang.

The images of submarine-launched missiles being pulled by vehicles made by Chinese company Sinotruk at Saturday’s parade revealed the difficulty in enforcing strict UN sanctions on the reclusive state.

About 80 percent of North Korean overseas trade - including essential food and fuel products – is with China, a signatory of sanctions which ban the export largely of goods which Pyongyang could use to build up its military.

Chinese Foreign Ministry spokesman Lu Kang said China conducts "normal" business with the North while adhering to UN Security Council sanctions which began in 2006.