Lee Jae-myung, chairman of the main opposition Democratic Party of Korea. (Yonhap)

A man has been sentenced to a fine of 500,000 won ($405.7) for scribbling offensive words last year on a presidential election campaign banner of now main opposition leader Lee Jae-myung, sources said Thursday.

The Seoul Western District Court recently gave the sentence to the 44-year-old man, surnamed Jin, charged with scribbling on a banner set up near a bus station in Seoul's Yongsan district last year to promote Lee's run in the latest presidential election, according to the sources.

Jin was charged with writing in February "Lee is guilty" and "fraudster" with a black marker on the banner that was promoting Lee as a presidential candidate well-versed in economy. He also scribbled letters to make the banner read Lee is well-versed in fraud and crimes.

The court ruled the messages damaged the utility of the banner designed to promote an election candidate's political pledges. It also said scribbling offensive words on an election banner goes beyond a voter's rights to voice opinion, rejecting Jin's claim that it was within his rights as a voter to state his opinion.

Under the Public Official Election Act, destroying election banners or signs can be subject to a prison sentence of up to two years or a fine of up to 4 million won.

The court also rejected Jin's petition to have the constitutionality of the official election act judged by the Constitutional Court.

Jin appealed the fine sentence on the day of the ruling. (Yonhap)