"I have no idea about what it will be like when I go to the North Korean side. It seems OK to be here, but we will be living there in a tense situation for a week," Kim Won-soo, a South Korean manager working in Kaesong, said before his departure Monday from Paju, South Korea.
While analysts call North Korea's threats largely brinkmanship, there is some fear that a localized skirmish might escalate. Seoul has vowed to respond harshly should North Korea provoke its military. Naval skirmishes in disputed Yellow Sea waters off the Korean coast have led to bloody battles several times over the years. Attacks blamed on Pyongyang in 2010 killed 50 South Koreans.
South Korea's new president, Park Geun-hye, is pursuing a policy that seeks to re-engage North Korea with dialogue and aid after five years of standoff. But she told her military Monday to set aside political considerations and respond strongly should North Korea attack.
Meanwhile, deputies to North Korea's Supreme People's Assembly gathered in Pyongyang. The SPA schedule Monday was unclear.
Under late leader Kim Jong Il, North Korea had typically held a parliamentary meeting once a year. But Kim Jong Un held an unusual second session last September in a sign that he is trying to run the country differently from his father, who died in late 2011.
Parliament sessions, which usually are held to approve personnel changes and budget and fiscal plans, are scrutinized by the outside world for signs of key changes in policy and leadership.
At a session last April, Kim was made first chairman of the powerful National Defense Commission, the body's top post.
On Sunday, Kim presided over a separate plenary meeting of the Central Committee of the ruling Workers' Party, which set a "new strategic line" calling for building both a stronger economy and nuclear arsenal.