The Democratic People's Republic of Korea (DPRK) was estimated to be on its way to miniaturizing nuclear weapons, the South Korean defense ministry said Friday.

"North Korea (DPRK) has conducted nuclear tests three times. Doubts still remain over whether (the DPRK) has a capability to make small, light (nuclear) warhead that can be mounted on missiles," Kim Min-seok, spokesman at the Ministry of National Defense, told reporters at a press briefing.

Kim, however, noted that the DPRK was estimated to be on its way to miniaturizing the nuclear warheads.

His comments came in response to media reports quoting US House Representative Doug Lamborn as telling a House hearing that the DPRK has the capability to deliver nuclear weapons with ballistic missiles. Lamborn cited a classified report by the Defense Intelligence Agency (DIA).

Pentagon spokesman George Little said in a statement that it would be "inaccurate" to suggest that the DPRK has fully demonstrated its capability to launch a nuclear-armed missile.

Neither the White House nor Chairman of the Joint Chiefs of Staff Martin Dempsey, who attend the hearing, has made any comments on the DIA assessment and Lamborn's statements.

Tensions have been running high on the Korean Peninsula after the DPRK conducted its third nuclear test on Feb. 12 in reaction to the joint military drills between Seoul and Washington.

Pyongyang said it would restart operations at its Yongbyon nuclear complex, including a uranium enrichment plant and a five- megawatt graphite moderated reactor that had been "mothballed and disabled" since October 2007 under an agreement reached at the six- party talks.