North Korean leader Kim Jong Un ordered the execution of the country’s vice premier, Choe Yong-Gon, earlier this year for criticizing his policies, South Korea’s Yonhap news agency reported Wednesday, citing an anonymous source.

Choe was executed by firing squad in May for expressing discontent over Pyongyang’s forestation policies, promoted by Kim, Yonhap reported, adding that Kim has tightened his grip on the country's leadership over the last few years, by systematically purging senior leaders he inherited from the regime of his father, Kim Jong Il, including the execution of nearly 70 officials.

Choe was appointed as North Korea’s new vice premier -- a senior cabinet position -- in June 2014. The state-run Korean Central News Agency reported at the time that Choe’s appointment brought the current number of the country’s vice premiers to seven. Choe previously served as vice minister of construction and building materials industries between 2004 and 2006.

However, Choe was not mentioned in the country’s state media since last October, suggesting that speculation about his execution could be true, Agence France-Presse reported. Choe’s death, if confirmed, would be the second execution of a top North Korean official reported this year.

Former defense chief Hyon Yong-Chol was said to have been executed in April by large-caliber anti-aircraft guns for reportedly falling asleep during a military parade attended by Kim. In late 2013, North Korea reportedly executed Jang Song-thaek, the husband of Kim’s aunt and once the country's second-most powerful figure, on charges of treason.