North Korean dictator Kim Jong-un has ordered more than 300 people to their deaths in the five years since he took power.

Mr Kim has used the executions to tighten his hold on power, according to the South Korean think-tank the Institute for National Security Strategy (INSS).

Some 140 of the 340 killed since 2011 were senior government officers.

North Korea Prison Camps Show all 7 1 /7 North Korea Prison Camps North Korea Prison Camps An overview of Camp 25 Amnesty International/DigitalGlobe North Korea Prison Camps The administration area of Camp 15 Amnesty International/DigitalGlobe North Korea Prison Camps A water treatment system in Camp 25 Amnesty International/DigitalGlobe North Korea Prison Camps Crop fields and, inset, prisoners in Camp 25 Amnesty International/DigitalGlobe North Korea Prison Camps The reported crematorium in Camp 25 Amnesty International/DigitalGlobe North Korea Prison Camps A possible mine Amnesty International/DigitalGlobe North Korea Prison Camps A walled compound in Camp 15 Amnesty International/DigitalGlobe

In August two officials were reportedly executed with an anti-aircraft gun on Mr Kim's orders - one for falling asleep in a meeting and the other for proposing a project the despot believed would challenge his authority.

Bruce Bennett, a defence analyst from the RAND Corporation think-tank told CNN Mr Kim had demonstrated an "extreme" level of brutality since inheriting his father's place as leader.

"For example, in the five years he has served as leader of North Korea, he has purged his defence minister five times, while his father changed his defence minister only three times in his 17 years. And two of those changes were because they died of old age,” he added.

The five-year tally surfaced in INSS' report "The misgoverning of Kim Jong Un's five years in power", released on Thursday.

Mr Kim's highest-profile execution was that, three years ago, of his uncle and one-time deputy Jang Song Thaek. He had about 50 officials executed in 2014 on charges ranging from graft to watching South Korean soap operas.