North Korea sparked international concern last week when it announced it would resume activity at its Yongbyon nuclear facility. The nuclear complex was closed in 2007 following multilateral negotiations.
U.N. Secretary-General Ban Ki-moon said from The Hague he was aware of heightened nuclear concerns, but had no specific information about potential test preparations.
"As I have already stated this morning here, I have been repeatedly urging the (the North Korean government) to refrain from taking any further provocative measures," he said in a statement to reporters Monday.
The South Korean government said Monday there was activity near a nuclear test site in North Korea, adding to growing concerns over recent war rhetoric. The South Korean Defense Ministry said the activity was normal, however, and not a sign of a pending test, the Yonhap news agency reports.
North Korea was criticized by the international community for a February underground nuclear test, it's third. Ban said Monday the North Korean government was challenging the authority of the U.N. Security Council, which censured North Korea for the February test.
The South Korean government said it will destroy North Korean nuclear facilities if it sees signs of an imminent nuclear attack, Yonhap adds.