President Lee Myung-bak on Monday vowed to “immediately exercise (Seoul’s) right of self-defense” if North Korea attempts military provocation again as he announced several countermeasures against the North, which allegedly sank a South Korean warship in March.

“From now on, the Republic of Korea will not tolerate any provocative act by the North and will maintain the principle of proactive deterrence,” Lee said during a televised national address, which was followed by a joint press briefing by the ministers of unification, foreign affairs and defense.

“If our territorial waters, airspace or territory are militarily violated, we will immediately exercise our right of self-defense.”

Lee defined the Cheonan’s sinking as “a surprise North Korean torpedo attack,” saying that it “constitutes a military provocation against the ROK.”

Admitting the mistakes made by the South Korean Armed Forces, Lee said his government will “solidify national security readiness.”

“The discipline of the Armed Forces will be reestablished, military reform efforts will be expedited and combat capabilities will be reinforced drastically,” he said during the 10-minute speech.

“ROK-U.S. joint combat readiness will be further strengthened on the basis of the strong ROK-U.S. alliance.”

As its first military measure to punish Pyongyang for the deadly attack, Seoul will launch its own antiproliferation exercise and resume psychological warfare against North Korea, Defense Minister Kim Tae-young said during a joint press briefing following the presidential address.

As another retaliatory step, North Korean vessels have been prohibited from sailing in South Korean waters, previously allowed under an inter-Korean maritime pact signed in 2004, Kim said.

The South will also launch a joint antisubmarine military exercise with the U.S. in the West Sea that focuses on improving defense tactics against the North’s underwater attacks.

Kim said South Korea would aggressively participate in the U.S.-led Proliferation Security Initiative in and out of the Korean Peninsula as part of an international effort to stop the shipment of weapons of mass destruction.

South Korea, after years of hesitation so as not to provoke the North, decided to join the PSI following North Korea’s nuclear and missile tests last year.

“The maritime interdiction training exercises within the region will be led by our Navy and are currently planned for the latter half of this year,” Kim said.

“We will also participate in a maritime interdiction exercise outside the region hosted by Australia in September this year.”

Acknowledging his military’s lax system that allowed the North’s torpedo attack, Kim said his military would improve its defense posture and learn lessons from the sinking.

Lee also announced other punitive actions against the North including a suspension of inter-Korean trade and exchange, mentioning the killing of a South Korean tourist by a North Korean armed guard at the Mount Geumgang resort in 2008, the North’s recent confiscation of South Korean assets in the resort and the Cheonan’s sinking which killed 46 South Korean sailors.

“Under these circumstances, any inter-Korean trade or other cooperative activity is meaningless,” he said.

Lee added, however, that Seoul will continue to provide assistance for children in North Korea.

“Matters pertaining to the Gaeseong Industrial Complex will be duly considered, taking its unique characteristics into consideration,” he said.

The punitive actions were explained in more detail by the ministers of unification, foreign affairs and defense during the joint press briefing.

In addition to the all-out prohibition of North Korean vessels’ operation or docking in South Korean waters, including the Jeju Strait, and suspension of inter-Korean trade, Unification Minister Hyun In-taek said Seoul will ban South Koreans’ visits to all areas in North Korea except for the joint venture in Gaeseong and limit their contact with North Koreans.

He also announced the prohibition of new investments or expansion of investments in existing projects in North Korea, while continuing production activities in Gaeseong.

Cross border aid programs will be generally deferred with the exception of aid for infants and children in North Korea, Hyun said.

As for the joint industrial park in Gaeseong, Hyun said Seoul “will not tolerate any harm done by the North to the safety of South Korean citizens.”

President Lee urged the North Korean authorities to apologize immediately to the ROK and the international community, and to immediately punish those who are responsible for and those who were involved in the sinking of the Cheonan.

“These are basic measures that the North has to take before anything else. If the North continues to make excuses and wild assertions as it has always done in the past, they will not find any place to stand in the world,” he said.

Lee also stressed that the North’s military provocation against the Cheonan on March 26 violated the Charter of the United Nations and contravened the existing agreements reached for the sake of peace and stability on the Korean Peninsula, including the Korean War Armistice Agreement and the Basic Agreement between South and North Korea.

“In close consultation with the nations concerned, the government will refer this matter to the U.N. Security Council, so that the international community can join us in holding the North accountable,” he said.

“Many countries around the world have expressed their full support for our position.”

His foreign minister Yu Myung-hwan said during the following press briefing that Seoul will launch an all-out diplomatic campaign to punish North Korea, saying its armed provocation “shattered peace on the divided peninsula and posed threats to global and regional security.”

Yu said that 21 nations around the world, including the United States, Japan, Britain, France, Australia, Canada and Sweden, have already issued statements denouncing the North and pledged their support for South Korea’s countermeasures. More nations and international organizations are expected to follow suit, he said.

In particular, Washington has been in close talks with Seoul over measures to punish Pyongyang, Yu said. The allies will have in-depth discussions on the issue when U.S. Secretary of State Hillary Clinton visits Seoul this week, he said.

South Korea has also been working with China and Russia, two of the five permanent members of the UNSC, Yu said.

“We believe the UNSC should deal with this issue as it is a matter that is directly related to international peace and security,” Yu said.

“We’re having close consultations with related nations on this.”

Yu said South Korea will call for greater international support in carrying out existing U.N. sanctions against the North in a more stringent manner to restrict the North’s illicit trade in arms.

The top diplomat also said that South Korea will consider playing a greater role in the PSI, a U.S.-led anti-proliferation campaign aimed at stopping rogue states like North Korea from spreading weapons of mass destruction. Pyongyang has bristled at the campaign, saying it is a U.S.-move to overthrow the regime.

The Foreign Ministry plans to discuss with the EU, the NATO and ASEAN possible countermeasures against the North’s provocations and to urge the international community to take actions to condemn or punish the North.

President Lee criticized the North for refusing to open up and make efforts to improve the welfare of its people, adding that he is “truly ashamed” as a compatriot.

“Nothing has changed over the last 60 years. It is a country still holding onto an empty ambition of forcefully reuniting the Korean Peninsula under the banner of communism,” he said.

“It is a country that still believes in making threats and committing terrorist activities. North Korea’s goal is to instigate division and conflict. For what reason and for whom is it doing what it does?”

Lee urged the North to “look at the reality and make that courageous decision,” referring to international demands for its denuclearization in exchange for economic aid.

“The Korean Peninsula must not be left standing as the danger zone in Northeast Asia,” he said.

“The two Koreas must take the initiative and resolve this problem. The peninsula must become a new cradle of world peace.”

Noting that the North has never officially admitted its past crimes such as the bombing attack against the presidential delegation at the Aung San Martyr’s Mausoleum in Myanmar and the bombing in midair of Korean Air Flight 858 during the Cold War era, Lee said this time was no different. Pyongyang has claimed that Seoul fabricated the sinking of the Cheonan.

“We have always tolerated North Korea’s brutality, time and again. We did so because we have always had a genuine longing for peace on the Korean Peninsula,” the president said.

“But now things are different. North Korea will pay a price corresponding to its provocative acts. I will continue to take stern measures to hold the North accountable.”

Addressing South Koreans and “our compatriots in North Korea,” Lee said “the overriding goal of the ROK is not military confrontation.”

“Our goal has always been the attainment of real peace and stability on the Korean Peninsula. Our goal is to bring about prosperity for all Koreans,” he said.

“Our vision is to realize the peaceful reunification of the Korean Peninsula.”

Lee’s national address on Monday came days after a multinational team of investigators concluded that North Korea sank the 1,200-ton South Korean warship Cheonan on March 26 with a heavy torpedo. The unprovoked attack claimed the lives of 46 South Korean sailors.

By Kim So-hyun  (sophie@heraldcorp.com)