South Korean opposition leader Lee Jae-myung was stabbed in the neck during his visit to Busan, a southeastern port city.
According to reports, the leader of the Democratic Party, South Korea's main opposition party, was attacked on the left side of his neck while engaging with reporters on Busan's Gadeok Island. Jae-myung was touring the construction site of the new airport in the island.
The attacker has been arrested at the scene.
The motive behind the attack is currently under investigation.
South Korean media cited witnesses as saying the man used a knife-like weapon to stab Lee's neck. TV video showed Lee lying on the ground with a person pressing a handkerchief to his neck to stop the bleeding.
The reports said the attacker was wearing something that looked like a crown on his head.
Lee lost the 2022 presidential election to President Yoon Suk Yeol by a narrow margin.
Lee, a liberal former provincial governor, is known for his outspoken style. His supporters see him as an anti-elitist hero who could reform establishment politics, eradicate corruption and solve growing economic inequality. Critics view him as a dangerous populist who relies on stoking divisions and demonizing his conservative opponents.
