The head of the National Police Agency(MPA) called for a thorough investigation into Tuesday's attack on main opposition Democratic Party(DP) leader Lee Jae-myung while on a visit to the southeastern port city of Busan.

In a statement, NPA Commissioner General Yoon Hee-keun said he has ordered the Busan Metropolitan Police to establish an investigation headquarters to promptly and thoroughly probe the incident for details such as the motive and existence of a mastermind.

The police chief has also pledged to reinforce security for prominent public figures to prevent additional attacks.

A suspect in his 60s or 70s lacerated the left side of Lee's neck after approaching him while pretending to be a supporter during the DP chief's inspection of the site of delayed construction for a new airport on Gadeok Island.

Lee was transported by helicopter to a hospital some 20 minutes after the attack, having received medical treatment on-site for a wound around one centimeter long, with the police saying that he was not gravely injured.

The suspect, who kept mum as he was taken into custody immediately after the attack, is exercising the right to remain silent.