The report added that the politician was stabbed in the neck after he visited the construction site of a new airport. The attacker was arrested at the scene of the incident, the report said.
South Korea is scheduled to hold legislative elections in April. The opposition party led by Lee controls the National Assembly. He recently ran for President in 2022, losing to current South Korean President Yoon-Suk-yeol by the smallest margin in South Korean history.
Lee is facing corruption charges stemming from his time as mayor of Seongnam, a satellite city of Seoul. Lee has denied the accusations and accused the prosecutors of being politically motivated.
President Yoon said that the attack on Lee was "unacceptable."
According to international media reports, Lee was transferred to a hospital about 20 minutes after the attack and was conscious at that time.