Seoul, South Korea (CNN) -- South Korea on Thursday warned North Korea of serious consequences if it rejects an offer to hold talks about the dire situation at their shared manufacturing zone where Pyongyang has halted activity amid recent tensions.
The South Korean Unification Ministry spokesman Kim Hyung-seok urged the North to respond to the offer of talks over the zone, the Kaesong Industrial Complex, by noon on Friday.
Kim said that if Pyongyang turns down the offer, Seoul would have no choice but to take "grave" measures. He did not specify what those measures might involve.
Seen as the last major symbol of cooperation between the two countries, the Kaesong complex is a joint economic zone on the North's side of the border that houses the operations of more than 120 South Korean companies.
Earlier this month, during a frenzy of fiery rhetoric directed at South Korea and the United States, the North began blocking South Koreans from entering the complex across the heavily fortified border.
It then pulled out the more than 50,000 North Koreans who work in the zone's factories, saying it was temporarily suspending activity there.
Since the North started preventing people from entering the zone from the South Korean side, the number of non-North Koreans in there has steadily dwindled from more than 800 before the crisis began.
As of Wednesday, 176 South Koreans and one Chinese person remained in the Kaesong complex, according to South Korean authorities.
CNN's K.J. Kwon reported from Seoul, and Jethro Mullen reported and wrote from Hong Kong.