North Korea's Supreme Court has convicted two South Koreans on state subversion charges and sentenced them to life in prison with labor.

The sentences for Kim Kuk-gi and Choe Chun-gil were handed down Tuesday after they were found guilty of spying for South Korea. Officials in South Korea have denied they were involved in espionage and demanded they be released.

North Korea presented the two before reporters in March and said they had been taken into custody last September and December.

Under North Korean law, the sentences are final and cannot be appealed.