The Korea Exchange activated a buy-side sidecar on the KOSPI on Thursday, suspending program trading in KOSPI-listed shares for five minutes at 9:58 a.m. after the benchmark rose 325.34 points, or 5.03%, to 6,790.39. The KOSPI had opened at 6,680.35 and was up 2.58% at 6,638.35 as of 9:04 a.m., after gaining as much as 3.23%, while the Kosdaq rose 2.66% to 846.42. The rally followed the U.S. Treasury's decision to double its long-term Treasury buyback program to at least $4 billion per operation from $2 billion, pushing yields lower and improving risk appetite. Retail investors led buying in South Korea, although foreign investors sold shares, indicating continued short-term profit-taking pressure. The sidecar is triggered when the KOSPI 200 Futures Index rises 5% or more for at least one minute.