Japan is urging China to do more to get North Korea to attend a new round of multi-party talks on its nuclear programs this month. Meanwhile, there have been reports of a huge detonation in North Korea near the border with China.
South Korean media reported Sunday on the explosion, saying it sent up a mushroom cloud 3.5 kilometers wide on Thursday, in North Korea, near a missile base.
South Korean Unification Minister Chung Dong-young downplayed the significance.
Mr. Chung says the cause of the blast is still to be determined, but he is doubtful it came from a North Korean nuclear-weapons test.
Meanwhile, Japan's foreign minister met with Chinese officials Sunday in Beijing, and urged them to do more to push North Korea back to the six-party talks on dismantling its nuclear programs.
Japanese spokesman Hatsushita Takashima said the explosion reports came up in conversations with the Chinese.
"That was touched upon, ? but they did not have any information, and we did not have any other information," Mr. Takashima says.
News of the explosion comes amid intense speculation that North Korea might be preparing for its first nuclear-weapons test.