March 13 (Bloomberg) -- North Korea shut its two southern border crossings for the second time this week, stranding almost 800 South Koreans and increasing tensions as the communist nation prepares to launch a rocket that the South says may be a missile.

Some 730 South Koreans, three Chinese nationals and an Australian are at North Korea’s Gaeseong Industrial Complex, South Korea’s Unification Ministry spokesman Kim Ho Nyoun told reporters today in Seoul. Those at Gaeseong were working for some of the 90 mostly South Korean companies with plants there, Kim said. The rest are trapped at the Mount Geumgang crossing.

“North Korea’s actions damage the mutual trust between the North and the South, and help neither side,” Kim said. “The South Korean government expresses its deep regret at the repetition of such actions, and urges North Korea to immediately return operations to normal.” It isn’t clear when the stranded people will be allowed to return to South Korea, he said.

North Korea shut the crossings March 9 to protest U.S.-South Korean joint military drills scheduled until March 20. More than 600 South Koreans were stranded until North Korea opened roads again the next day. The U.S. and South Korea described the annual exercise as “purely defensive,” while North Korea said it is preparation for a pre-emptive strike on Kim Jong Il’s regime.

The crossing points into North Korea are reached by narrow corridors between the countries through the mine-strewn demilitarized zone along the 39th parallel. Travelers must have North Korea’s permission to cross and be accompanied by North Korean military escorts.

Long-Range Missile

Tensions between the countries, which haven’t signed a formal peace treaty since their 1950s conflict, have increased in recent weeks. South Korean officials have said they suspect North Korea may test a Taepodong-2 missile capable of reaching Alaska. North Korea said the launch, scheduled for the April 4-8 period, will put a communications satellite into space.

South Korea Foreign Minister Yu Myung Hwan today urged North Korea not to go ahead with the move, saying any launch will have to be discussed at the United Nations Security Council because it will have breached a resolution passed in 2006.

The International Maritime Organization and the International Civil Aviation Organization confirmed yesterday that North Korea had alerted them of its plans to fire a rocket next month. UN Secretary-General Ban Ki-moon said the launch “would threaten regional peace and security” and might violate Security Council resolutions.

The U.S. and Japan have also urged North Korea not to carry out the launch. China’s Premier Wen Jiabao today advised nations involved in six-party talks on dismantling North Korea’s nuclear weapons program to avoid raising tensions.

Kim’s regime agreed in February 2007 to scrap its nuclear program in return for energy aid and normalized diplomatic ties with the U.S. and Japan. Six-nation disarmament talks are currently stalled with North Korea refusing to let inspectors remove samples from its Yongbyon reactor, the source of the country’s weapons-grade plutonium.

To contact the reporter on this story: Heejin Koo in Seoul at hjkoo@bloomberg.net.

Last Updated: March 13, 2009 07:02 EDT