The head of South Korea's main opposition party, Lee Jae-myung, was stabbed in the neck on Tuesday, officials said.

Lee was attacked by an unidentified assailant while touring the site of a proposed airport in the southern city of  Busan.

Lee's Democratic Party's spokesperson Kwon Chil-seung said that the politician had undergone surgery. 

He "is currently admitted to the intensive care unit and is recovering," according to the spokesperson.

The official also said the opposition politician had suffered "damage to the internal jugular vein," but was conscious following surgery.

In the immediate aftermath of the attack, there was concern over the large amount of bleeding that Lee suffered.

President Yoon Suk Yeol ordered a speedy investigation and offered his support to Lee, the president's office said in a statement.

"Yoon emphasized our society should never tolerate this kind of act of violence under any circumstances," the statement added.

What we know about the attack

Local news reports said the attacker appeared to be a man in his 50s or 60s who approached Lee for an autograph.

The attacker then suddenly lunged forward and appeared to stab the opposition leader in the left side of his neck.

Officials near Lee quickly subdued the attacker before police officers detained him, senior Busan police officer Sohn Jae-han said in a televised briefing.

Sohn said 41 police officers had been deployed to the area for crowd control and traffic management.

Photos of the incident show Lee on the ground with his eyes closed, with people around him pressing a handkerchief against his neck.

Police said Lee suffered a "one-centimeter laceration on his neck," according the Chosun Ilbo newspaper.

He was subsequently airlifted to hospital. 

Police said that they had seized an 18-centimeter (seven-inch) knife used by the attacker.

Busan police official Son Je-han was cited by the Reuters news agency as saying that the knife was bought online. He said that the motive was still being investigated.

Parliamentary elections on the horizon

Lee heads South Korea's Democratic Party. He lost the 2022 presidential election to nationalist Yoon by a narrow margin.

South Korea's parliamentary elections are slated for April.

While the Asian country has strict gun control, it also has a history of political violence involving other weapons.

Last year, Lee's predecessor Song Young-gil was attacked at a public event by an assailant who swung a blunt object against his head.

Conservative former President Park Geun-hye was also attacked with a knife at an event in 2006 when she was still opposition leader. 

rm, zc/kb (Reuters, AP, AFP)