North Korea threatened Sunday to carry out a "new form" of nuclear test in response to a U.N. condemnation of the North's recent ballistic missile launches.

North Korea test-fired two ballistic missiles into the sea off its east coast on Wednesday, drawing international condemnation for its violation of relevant U.N. Security Council resolutions.

The Security Council condemned the launches the following day, saying it was considering an "appropriate response". It stopped short of issuing a formal statement or imposing penalties on the North.

"It (North Korea) would not rule out a new form of nuclear test for bolstering up its nuclear deterrence," the North's foreign ministry said in an English-language statement carried by state media Korean Central News Agency, monitored in Seoul.

The statement also warned the U.S. against "acting rashly," saying Washington will bear all responsibility in the event of a "catastrophic" event on the Korean Peninsula.

"It is quite natural for the KPA to make full preparations to cope with the prevailing grave situation as its mission is to protect the security of the country and its people and defend peace," the statement said, referring to the Korean People's Army of North Korea.

"If the UNSC persistently tries to deny the exercise of the DPRK's just right by partially citing the unreasonable 'resolutions' according to the U.S. scenario, it will end up escalating tensions and sparking conflict only, far from contributing to keeping peace and security on the Korean peninsula and in the region."

DPRK is the acronym of North Korea's official name, the Democratic People's Republic of Korea.

The missile launches came hours after the leaders of South Korea, the U.S. and Japan met on the sidelines of a nuclear security summit in The Hague, the Netherlands, and urged the communist nation to give up all of its nuclear programs in a complete, verifiable and irreversible manner.

South Korea's defense ministry said the launches appeared to be in protest of international pressure to denuclearize as well as the ongoing joint military exercises between Seoul and Washington, which Pyongyang has long condemned as preparation for a nuclear war against it.

South Korea and the U.S. insist that the annual drills are defensive in nature.

Earlier in the day, North Korea resumed its harsh criticism of South Korean President Park Geun-hye.

Quoting a military officer, the North's main newspaper Rodong Sinmun said Park's recent calls for unification, co-prosperity and exchanges with the North during her visits to the Netherlands and Germany last week were nonsense.

"We see clearly through the obvious, crafty mind of Park Geun-hye, who is going out of her mind to harm us as she wears a smile on her face but bears poison in her heart," the paper said.

On Saturday, a spokesman for the North Korean delegation to high-level inter-Korean contacts mentioned Park's name numerous times as he accused the South of spreading anti-North Korea leaflets near the western sea border.

On Sunday, Seoul demanded Pyongyang immediately stop its "vulgar remarks" and "slander" of the president, saying it will keep a close eye on the North's actions.

"As we have said numerous times, our government has never slandered North Korea," the South Korean government said in a statement. "It is clear that we cannot restrict the freedom of expression of our civic groups and press, which is guaranteed by the Constitution, without legal grounds." (Yonhap)