Story highlights State media reports prosecutor demanded 15 years of hard labor, he was given 10

North Korea alleges Kim Dong Chul spied for South Korea to steal nuclear and military secrets

Kim is a South Korean-born American citizen

(CNN) North Korea has sentenced a South Korean-born American citizen to 10 years of hard labor for subversion and espionage, a North Korean official told CNN.

Prosecutors were seeking a 15-year hard labor sentence for Kim Dong Chul for committing "offenses in a scheme to overthrow the socialist system of the DPRK," according to state-run news agency KCNA.

The defense asked that Kim's sentence be commuted, arguing "the crimes by the accused are very serious but he is old and may repent of his faults."

Friday's verdict was handed down by North Korea's Supreme Court.

The U.S. State Department said it is aware of the media reports about Kim's sentence.