South Korean media say the government is monitoring suspicious activities at a North Korean nuclear site where Pyongyang carried out its first nuclear test earlier this month.

The reports quote South Korean military sources as saying Pyongyang is building a new structure at the Punggye-ri site in North Korea's remote northeast. But, the sources say the purpose of the facility is unclear.

The reports say South Korean intelligence agencies are closely watching movements of trucks and soldiers in the area to see if they are preparations for a second nuclear test, or just a deception.

South Korean media have reported several cases of suspicious movements at the nuclear site since the first test on October 9. But, South Korean officials have said they have no information that another test is imminent.

South Korean Foreign Minister Ban Ki-moon - soon to be the new U.N. secretary-general - met with Chinese leaders in Beijing Friday to discuss sanctions against North Korea for conducting the first test.

China's official Xinhua news agency says Ban met with President Hu Jintao, Foreign Minister Li Zhaoxing and State Councilor Tang Jiaxuan. Tang had talks last week with North Korean leader Kim Jong-il.

Details of Friday's discussions were not immediately released.