Yonhap said the 59-year-old suspect had previously served a four-year prison sentence for attempted murder.
The suspect has been fitted with an electronic monitoring ankle bracelet since his release in 2019, and had been receiving treatment for mental health issues and alcohol addiction, the Justice Ministry said in a statement.
The electronic monitoring system is a crime prevention programme that covers people convicted of a range of crimes including murder.
The ministry pledged to conduct a thorough investigation of the system, which uses real-time GPS tracking to monitor high-risk offenders after their release from prison.
Incheon, west of Seoul, is home to South Korea’s main airport and forms part of the wider Seoul metropolitan area.
South Korea is generally considered a safe country, with a homicide rate of 1.3 per 100,000 people in 2021, according to official statistics, well below the global average of about six per 100,000.
The country has, however, seen a number of stabbing attacks in recent years.
