SEOUL - Lee Jae-myung, leader of South Korea's main opposition Democratic Party, was injured on Tuesday after being stabbed in the neck by a man in his 60s during a visit to the southeastern port city of Busan.

While taking questions from reporters at about 10:27 am local time (0127 GMT) after touring the construction site of a new airport in Busan, Lee was stabbed on the left side of his neck and collapsed on the floor with blood.

Citing the medical staff in Busan, a Democratic Party spokesman said in a televised press briefing that Lee's jugular vein, which carries blood from the head to the heart, was believed to have been damaged.

An unnamed Busan hospital official was quoted by Yonhap news agency as saying that if the carotid artery, which supplies blood to the head, was damaged, it would have become a life-threatening injury.

Lee reportedly suffered a laceration of around one and a half centimeters.

He was transported by helicopter to a hospital in Seoul for surgery after receiving an emergency treatment in Busan.

Video footage showed that the assailant approached Lee asking for an autograph and stabbed him in the left neck. People around Lee wrestled the attacker to the ground before the police arrested him at the scene.

About 20 minutes after the attack, Lee was taken to a nearby hospital in a conscious state.

The assailant, identified only with his surname of Kim in his 60s, told the police that he had the intention of killing the Democratic Party leader, local media reported citing the Busan metropolitan police agency.

Kim purchased the knife about 18 centimeters long on the internet last year. He had no other criminal record.

South Korean President Yoon Suk-yeol ordered the police and relevant authorities to rapidly find out the truth and make every effort to support Lee for his treatment, according to the presidential office.

Yoon stressed that such violent acts should never be tolerated under any circumstances.