The comments came as the two sides opened a second day of talks on further developing their joint industrial complex in the North, and were likely to draw an angry reaction from Pyongyang, which recently issued its own threat to break off dialogue with Seoul and attack.
South Korea should "immediately launch a strike" on the North if there is a clear intention of a pending nuclear attack, Defence Minister Kim Tae-young said at a seminar in Seoul.
Kim made similar remarks in 2008 when he was chairman of South Korea’s Joint Chiefs of Staff, prompting North Korea to threaten South Korea with destruction.
The North, which conducted underground nuclear tests in 2006 and 2009, claims its nuclear weapons are not for use against South Korea, but rather are a security guarantee against what it claims is US hostility.
Despite the rhetoric from both sides, officials held follow-up discussions yesterday on the industrial complex in the North’s border city of Kaesong, according to Seoul’s Unification Ministry. It did not provide further details.
The South Korean delegation was scheduled to return home last night, said Unification Ministry spokesman Chun Hae-sung.
On Tuesday, they met for nearly four hours to assess their joint tour of industrial parks in China and Vietnam undertaken in December.
Chun had described the talks as taking place "in a serious and practical atmosphere".
Seoul stressed the need for a quick and easy system for border crossings and customs clearance for South Koreans who travel to and from the industrial park, Chun said, in an apparent call on the North to improve the system.
The North said their recent surveys in China and Vietnam offered an opportunity to revitalize the complex, Chun said.
Kaesong, which combines South Korean capital and technology with cheap North Korean labor, is the most prominent symbol of inter-Korean cooperation.
About 110 South Korean factories employ some 42,000 North Korean workers.
The complex came under a cloud in late 2008, however, when North Korea tightened restrictions on border crossings amid growing tensions between the two countries.
This week’s talks came just days after Pyongyang threatened to launch a "sacred nationwide retaliatory battle" and vowed to cease all communication with the South following reports of a South Korean contingency plan to handle any unrest in the isolated North.