North Korea executed Vice-Premier Choe Yong-gon for opposing the forestation policy of the country's leader, Kim Jong-un, according to reports that claim the 63-year-old was killed in May. He was a former delegate of the North-South cooperation group and South Korea's Unification Ministry said it is looking into the speculation as the vice-premier "has been missing from the public eye for some time now".

"Choe has not been seen publicly for about past eight months since he was last witnessed in December last year at the ceremony to mark the third anniversary of the death of North's former leader Kim Jong-il. The government is closely watching to see what might have happened to him," it said in a statement, as reported by South Korea's Yonhap news agency.

However, the news agency claimed that since Choe Yong-gon expressed disagreement with Kim's forestry policies and had shown "poor work performance", he was executed by firing squad.

North Korea's state-run KCNA news agency had earlier said Choe Yong-gon, who had worked on inter-Korean affairs in early 2000, lead the country's delegation in joint economic cooperation committees with South Korea between 2003 and 2005, was appointed vice-premier in 2014.

In May, reports claimed North Korea had executed its then defence chief Hyon Yong-chol, by putting him in front of an anti-aircraft gun. If Choe Yong-gon's execution is confirmed, it would put the number of senior officials executed since Kim Jong-un took charge of the country at 70.