TOKYO — Japan has evidence that a Chinese company exported to North Korea vehicles capable of transporting and launching missiles, in possible violation of U.N. sanctions, Japanese media reported today.

China called the reports inaccurate, and denied violating any U.N. restriction.

The U.S., which has previously said it took China at its word that it was complying with the sanctions, said Wednesday that in recent weeks it has raised with Beijing allegations that Chinese companies assisted North Korea’s missile program.

According to the Japanese reports, four of the vehicles were shipped from Shanghai to North Korea last August aboard the Harmony Wish, a Cambodian-flagged cargo vessel. Japanese authorities tracked the ship by satellite, and searched it after it had delivered its cargo, when it transited through Japan the following month, the reports said.

Such vehicles — called TELs, for transporter, erector, launcher — became the focus of international attention when North Korea displayed what looked like several of them during a military parade in its capital, Pyongyang, in April.

They are a concern because they could give the North the ability to transport long-range missiles around its territory, making them harder to locate and destroy.

Japan’s top government spokesman declined to confirm the reports Wednesday. But he said that if necessary, Japan would work with the international community to determine if U.N. regulations were violated.

In Beijing, Liu Weimin, a spokesman for China’s Foreign Ministry, said his country has not violated any restrictions.

“Chinese companies did not violate U.N. and Chinese laws,” he said, calling the reports “inaccurate.” He did not specifically confirm or deny the vehicles were sold, but said China is opposed to proliferation and is “complying with U.N. laws and regulations.”

Although no suspicious vehicles were aboard the ship when it was searched in Japan, authorities found documents detailing the cargo it had unloaded in North Korea, and that included the vehicles, according to the Asahi, a major Japanese newspaper. It cited multiple but unnamed government sources.

It said the exported vehicles were believed to have been the ones used in the military parade, which was held shortly after a North Korea rocket launch that was widely condemned as an attempt to develop its long-range missile technology. The rocket, which North Korea claimed carried a satellite, failed soon after liftoff.

NHK, Japan’s public broadcaster, and other media later had similar reports, also citing unnamed government sources.

The Asahi said the evidence was shared with South Korea and the United States, but claimed that Washington requested it not be made public.

On April 19, after press reports on the possible Chinese origin of the launch vehicle displayed in the military parade, U.S. State Department deputy spokesman Mark Toner said that China had provided repeated assurances that it was complying with the U.N. sanctions.

“I think we take them at their word,” he said.

But at a news conference Wednesday, department spokeswoman Victoria Nuland said the U.S. in recent weeks has raised with Beijing its concerns over allegations of Chinese entities assisting North Korea’s missile program. She said the U.S. would continue to work with China and others in the international community on enforcing the sanctions. She refused to give further details as it pertained to intelligence, which the department refrains from commenting on.

Asahi identified the Chinese exporter as Wuhan Sanjiang Import Export Co., a subsidiary of state-owned China Aerospace Science and Industry Corp., and the North Korean importer as Rimmok General Trading, which it said was likely a front company.

Immediately after the parade, private experts said the vehicles probably came from China, citing similarities to Chinese design patterns in the windscreen, the windscreen wiper configuration, the door and handle, the grill, the front bumper lighting configurations, and the cabin steps.

Despite the latest reports, experts say pinning a sanctions-busting charge on Beijing would be difficult because it would be hard to prove that Beijing knowingly approved the exports for military purposes.

With different modifications, the vehicle can also be used in commercial fields. The Asahi report said that China claims the vehicles were to be used to carry lumber.

The U.N. Security Council imposed sanctions against North Korea after its first nuclear test in 2006 and stepped up sanctions after its second test in 2009 to try to derail the country’s rogue nuclear weapons and ballistic missile programs. The sanctions restrict exports of weapons or technology that could be used to boost those programs.