The Foreign Ministry says North Korea's reported construction of a light-water nuclear reactor, if confirmed, would be a blow to the international community's hope that Pyongyang might abandon its nuclear ambitions.

Ministry spokesman Kim Young-sun on Monday told a regular news briefing that the North promised to give up all nuclear weapons and nuclear-related programs in a 2005 agreement.

Kim added that it is important for the North to sincerely carry out the promise and abide by international obligations for peace and stability on the Korean Peninsula.

The spokesman said that although the North repeatedly claimed last year that it would build a light-water reactor with its own technology, the South has no information about the North's capabilities in terms of reactor construction.

Kim added that Seoul is closely watching moves in the North while sharing information with other nations.