South Korea's foreign minister warned North Korea Thursday of "unbearable costs" for its nuclear weapons development as the communist country carried out further tests of its ballistic missile technology.

Foreign Minister Yun Byung-se issued the warning a day after the North fired two intermediate-range ballistic missiles off its east coast in a show of defiance against international sanctions aimed at curbing its nuclear and missile programs.

"As long as North Korea continues to defy the non-proliferation regime, we, the whole world, should remind North Korea that its misbehavior will have unbearable costs," Yun said in a speech before delegates from the 48 member nations of the Nuclear Suppliers Group. The NSG, which includes the United States, China and Russia, places controls on nuclear exports to ensure the non-proliferation of nuclear weapons.

The minister did not elaborate on what the "unbearable costs" could be. In March, the U.N. Security Council adopted its toughest-yet sanctions against North Korea in response to its fourth nuclear test in January and its long-range rocket launch the following month. Yun urged the international community to "fully and thoroughly" implement the sanctions resolution.

"The NSG needs to send a clear, loud and powerful message against North Korea's nuclear weapons programs, the number one threat to the international non-proliferation regime at this critical juncture," Yun said in his first public comments since Wednesday's missile tests.

Earlier Thursday, the North claimed success in the launch of the second Musudan missile, which it said flew 400 kilometers before landing in targeted waters in the East Sea.

The North has pursued missile and nuclear development in tandem, vowing to build nuclear-tipped ballistic missiles capable of reaching the U.S. mainland.

Prior to Wednesday's tests, the North launched four Musudan missiles, but all of them failed. In New York, the Security Council held an emergency meeting to discuss the latest launches.

Alexis Lamek, deputy U.N. ambassador of France that holds the council's rotating presidency for June, told reporters after the meeting that the council plans to adopt a press statement in the coming days. He also said council members recognized the launches are a violation of U.N. resolutions. (Yonhap)