The 67-year-old man who stabbed the leader of South Korea's opposition Democratic Party in January has been sentenced to 15 years in prison by a court on Friday, according to reports by the Yonhap news agency.

In a sentencing hearing at the Busan District Court, a judge said the crime which took place ahead of a general election was a serious challenge and an attempt to destroy representative democracy, according to Yonhap's report.

Prosecutors had sought a 20-year prison sentence for the attacker, which Yonhap named as Kim, but did not give his first name.

Lee Jae-myung, who recently resigned as Democratic Party leader, was stabbed in the neck while visiting the southern city of Busan in January.

Video footage showed a man wearing a paper crown with Lee's name on it, approaching Lee and asking for an autograph before lunging forward and stabbing him in the neck.

The attack was condemned as an "act of terror" and a challenge to democracy by President Yoon Suk-yeol and politicians from both the ruling and opposition parties.

Lee's party scored a landslide victory in a parliamentary election in April, dealing a resounding blow to President Yoon and his conservative party but fell short of a super majority.

Lee narrowly lost the 2022 presidential election and is on trial on bribery charges he denies.