North Korean leader Kim Jong Un visits the Kumsusan Palace of the Sun to mark the 21st anniversary of the death of founder Kim Il Sung in this undated picture released by North Korea's Korean Central News Agency (KCNA) on July 8, 2015. Reuters

Kim Jong Un’s “reign of terror” has seen over 70 executions of people deemed as a threat to the North Korean leader, according to South Korea’s foreign minister Yun Byung-se. Kim came to power in late 2011 after the death of his father, Kim Jong Il.

The younger Kim has overseen several brutal executions, many of which reportedly included being forced to stand in front of the barrel of an anti-aircraft machine gun, and being targeted by a mortar round.

“It is a sevenfold increase, compared with the first three years of Chairman Kim Jong-II's leadership. It's extremely unusual,” South Korea’s Yonhap news agency quoted Yun as saying at a forum in Seoul on Thursday.

Yun described Kim's regime as a “reign of terror” that has prompted more North Koreans to defect to the South, the Associated Press (AP) reported, adding that Yun did not reveal how he obtained the details.

According to South Korea's National Intelligence Service, however, the number of executions since Kim assumed leadership of North Korea may be as high as 90, Yonhap reported, adding that the reason behind the discrepancy in the reported numbers is unclear.

Kim has removed several key members of the old guard through a series of purges over the past three-plus years. The 2013 execution of his uncle, Jang Song Thaek -- for alleged treason -- was considered to be one of the most significant purges by Kim to date.

In May, the South Korean spy agency revealed that Kim ordered the execution of his then-defense chief Hyon Yong Chol with an anti-aircraft gun for complaining about Pyongyang’s authority and sleeping during a meeting. Kim also reportedly executed his aunt, Kim Kyong Hui, who was poisoned last year after she complained for months about the death of her husband, Jang.