North Korea used China-made trucks to display missiles at last Saturday's parade marking the 105th anniversary of founding president Kim Il Sung's birth, underlining the difficulty in enforcing UN sanctions against the isolated state.

Six Pukguksong submarine-launched ballistic missiles were towed behind trucks bearing the logo of Sinotruk, a Chinese company.

A Sinotruk sales official said yesterday he was not aware the company's trucks had been used.

When asked, Chinese Foreign Ministry spokesman Lu Kang said the two countries maintain "normal contacts, including normal business contacts", and that "as a permanent member of the UN Security Council, China strictly adheres to its international responsibilities, including those from Security Council resolutions".