South Korean police have raided the home and office of a man who stabbed the country’s opposition leader, Lee Jae-myung, in the neck in an attack that left him in intensive care, officials said.

The attack happened as Mr Lee was passing through a throng of journalists after visiting the proposed site of a new airport in the south-eastern city of Busan on Tuesday.

The attacker, posing as a supporter, approached the 59-year-old and asked for his autograph before taking out a 7in (18cm) knife.

After receiving emergency treatment in Busan, Mr Lee was taken by helicopter to the Seoul National University Hospital for surgery.

Cho Jeong-sik, the Democratic Party of Korea’s secretary-general, said on Wednesday that the two-hour operation was successful and that Mr Lee was recovering in intensive care.

Local media reports later said Mr Lee has been transferred to an ordinary ward.

Kang Cheong Hee, a cardiothoracic surgeon who is a Democratic Party member, later told a briefing that Mr Lee had suffered “a serious injury” – a cut of more than 0.35in (9mm) on his jugular vein.

Mr Kang, who did not operate on Mr Lee, said: “Lee was initially in a very critical condition and it’s no exaggeration to say he’s survived by divine luck.”

Police and emergency officials earlier said Mr Lee was conscious after the attack and was not in a critical condition.

The suspect was detained by police immediately after the attack. Officers said he told investigators he had been attempting to kill Mr Lee and that he had plotted his attack alone, but his motive is unknown.

Busan police said they sent officers to search the suspect’s home and office in the central city of Asan on Wednesday as part of their investigation.

Police said they plan to ask for a formal arrest warrant for the suspect over alleged attempted murder.

Police disclosed few further details about the suspect except that he is about 67 years of age and bought the climbing knife online.

They refused to say what kind of office he has in Asan, but local media photos showed officers searching a real estate office.

One of the suspect’s neighbours, who said he has known him for about two years, described him as a quiet, shy man who rarely spoke about politics.

He told the Associated Press that the suspect runs a real estate agency in Asan but is several months behind on his rent.

Mr Lee is a tough-speaking liberal who lost the 2022 presidential election to President Yoon Suk Yeol by 0.7 percentage points, the narrowest margin recorded in a South Korean presidential election.

Their closely fought presidential race and post-election bickering between their allies have deepened South Korea’s already-toxic conservative-liberal divide.

Police said officers searched the Seoul headquarters of Mr Lee’s Democratic Party and Mr Yoon’s People Power Party on Wednesday to confirm whether he has had a membership of either of the two parties.

Recent public surveys have put Mr Lee as one of two leading early favourites for the next presidential election in 2027, along with Mr Yoon’s popular former justice minister, Han Dong-hoon. Mr Yoon is barred by law from seeking re-election.

In a New Year meeting involving top officials, politicians and general citizens on Wednesday, which Mr Lee had been due to attend, Mr Yoon repeated his wish for his quick recovery.

He also condemned the stabbing as “a terrorist attack” that is “an enemy to all of us and an enemy to liberal democracy”, according to his office.

Mr Lee has been a vocal critic of Mr Yoon. Last year, he launched a 24-day hunger strike to protest at the president’s major policies, including what he called Mr Yoon’s refusal to firmly oppose Japan’s release of treated radioactive wastewater from its crippled Fukushima nuclear power.

Mr Lee has been grappling with a prolonged prosecutors’ investigation over a range of corruption allegations. He has denied legal wrongdoing and accused Mr Yoon’s government of pursuing a political vendetta.