North Korea is threatening to use terrorism against the South, Seoul’s intelligence agency said in a rare public advisory on Monday, and warned South Korean citizens in China and Southeast Asia to be on their guard. The attacks may be in retaliation for the recent airlift of a large group of North Korean refugees, the National Intelligence Service said. South Korea secretly organized the airlift of more than 460 North Korean refugees last month from a country that activists said was Vietnam. Full Story