South Korea, the U.S. and Japan last year discovered that China exported missile launch vehicles to North Korea, but they did nothing to hold Beijing to account, the Asahi Shimbun reported Wednesday.

Japanese naval security officials confirmed after seizing the shipping records of a Cambodian vessel anchored in Osaka port on Oct. 3 last year that a Chinese arms manufacturer run by the People's Liberation Army exported four WS51200 missile launch vehicles from Shanghai to North Korea’s Nampo port in August 2011.

The 16-wheeler missile launch vehicles were apparently manufactured by modifying an existing vehicle to carry China's Dongfeng-31 intercontinental ballistic missile, which has a range of around 8,000 km. North Korea unveiled eight 16-wheeler missile launch vehicles carrying ballistic missiles during a military parade in Pyongyang on April 15.

The Japanese daily said South Korea, the U.S. and Japan concluded at the time that China's export of the vehicles violated UN Security Council Resolution 1874, which bans arms sales to North Korea. But they did not seek UN sanctions since they needed China's cooperation in trying to curb North Korea's nuclear weapons program.

Japanese Foreign Minister Koichiro Gemba refused to confirm or deny the report. "I cannot comment, since the problem is related to intelligence reports," Gemba said. But he added China must strictly adhere to UN Security Council resolutions.

Chinese Foreign Ministry spokesman Liu Weimin told a regular press conference that the report was "inaccurate."