The Asahi Shimbun report -- based on Japanese government sources -- is the most strident of recent claims that China has been involved in helping to arm its wayward ally Pyongyang.
"China has been strictly implementing relevant Security Council resolutions and its own laws and regulations on non-proliferation export control," foreign ministry spokesman Liu Weimin said in response to a question on the report.
"Chinese companies did not export items that are banned by relevant Security Council resolutions or Chinese laws and regulations."
Asked whether China may have exported the vehicles through companies from third countries, Liu refused to comment further.
The sale of weapons systems to nuclear-armed North Korea is banned under resolutions passed by the UN Security Council, of which China is a veto-wielding permanent member.
The Asahi report said a subsidiary of China Aerospace Science and Technology Corp. -- affiliated to the Chinese military -- last August exported four trucks capable of transporting and launching ballistic missiles to North Korea.
The vehicles were probably those on show at a huge military display in Pyongyang in April marking the centenary of the birth of the state's founder Kim Il-sung, the report said.
But at Washington's urging, Tokyo and Seoul have avoided confronting Beijing over the issue in a bid to keep North Korea's patron onside in the international effort to contain tensions on the peninsula, it added.