South Korean opposition leader Lee Jae-myung has been airlifted to hospital in Seoul after he was stabbed in the neck by a man during a visit to the southeastern port city of Busan.

Lee, who heads the main opposition Democratic Party, was stabbed on the left side of his neck by a man who lunged out of the crowd as he was walking with journalists on Tuesday morning. Emergency officials have said he is not in a critical condition, although his exact status is unknown.

Pictures in South Korean media showed Lee, 59, lying on his back on the ground with his eyes closed as officials crowded around him and one pressed a cloth against his neck.

Democratic Party spokesperson Kwon Chil-seung said the politician was being flown to Seoul National University in the capital after receiving emergency treatment at Pusan National University Hospital.

Medical staff at the latter hospital suspected damage to a jugular vein that carries blood from the head to the heart. “There is concern that there could be large haemorrhage or additional haemorrhage, according to medical staff,” Kwon said.

The attack, seen in video footage and photographs, unfolded while Lee was touring the site of a proposed airport in Busan.

The assailant, wearing a paper crown reading “I’m Lee Jae-myung”, initially approached the politician asking for an autograph.

Videos circulated on social media showed the suspect being chased and tackled by several people, apparently including plainclothes police officers.

In a televised briefing, senior Busan police officer Sohn Jae-han said the suspect, aged about 67, told investigators that he bought the 18cm (7-inch) knife online.

However, the suspect has refused to answer police questions about his motives, according to the daily Busan Ilbo.