South Korean government condemned Monday the DPRK's nuclear test, saying it is a "serious threat and a "challenge", a spokesman of the presidential office said.

Lee Dong-kwan, spokesman of the presidential office, said on an official governmental statement that the current nuclear test conducted by the Democratic People's Republic of Korea (DPRK) is never acceptable as it is clearly in breach of the United Nations Security Council (UNSC) Resolution 1718, which banned any nuclear program on the Korean Peninsula.

South Korean President Lee Myung-bak called the test a "disappointment" and asked for the government to take 'swift' and ' thorough' countermeasures, according to the spokesman.

President Lee is schedule to call Japanese Prime Minister Aso Taro to discuss over the issue, followed by additional telephone calls to other leaders of the nation's allies.

DPRK has confirmed that it conducted an underground nuclear test earlier on Monday.

(Xinhua News Agency May 25, 2009)