REUTERS - North Korea's vice premier was executed by firing squad this year after showing discontent with the policies of the country's leader Kim Jong Un, a South Korean media report said on Wednesday.

Yonhap News Agency cited an unnamed source as saying that the 63-year-old Choe Yong Gon, a former delegate for North-South cooperation, was executed, marking another death of a senior official in a series of high-level purges since Kim Jong Un took charge in late 2011.

The Yonhap report said Choe had expressed disagreement with Kim's forestry policies in May and had shown poor work performance. It provided no further details.

South Korea's Unification Ministry, which handles the country's ties with North Korea, said in a text message received by Reuters that Choe had not been spotted in public for about eight months, and that it was closely monitoring the situation.

Open gallery view A man watches a TV news program reporting that North Korean defense chief Hyon Yong Chol was killed by anti-aircraft gunfire, at a railway station in Seoul, South Korea, May 13, 2015. Credit: AP

South Korea's National Intelligence Service declined to comment on the report to Reuters.

The South Korean spy agency told lawmakers in May that North Korea had executed its defense chief by putting him in front of an anti-aircraft gun at a firing range.

Choe was appointed vice-premier last year, North Korea's state-run KCNA news agency reported previously.

Yonhap said the source also said the reclusive state had publicly executed a senior Workers' Party official in September.

Choe had worked on inter-Korean affairs in 2000s, leading the North's delegation in joint economic cooperation committees with South Korea between 2003 and 2005.

He attended the 2004 opening ceremony of the Kaesong Industrial Complex, a factory park jointly run with Seoul that is the last remaining joint project of the two countries.