Mr Kim, who died from a heart attack at the age of 69, had led the nation since 1994. He had been unwell for several years.

It was announced a year ago that his son Kim Jong-un would become head of state on his father’s death.

Kim Jong-un is the youngest of the leader’s three sons. It is not known exactly how old the new leader is, although he is thought to be in his late twenties.

North Korea is a communist nation, which is known for being very secretive. The nation became even more isolated because Kim Jong-il was trying to build up a supply of nuclear weapons.

There is now concern that the change of leader, combined with the fact that the new leader is very young, could bring trouble.

Professor Lee Jung-hoon from Yonsei University in Seoul, South Korea, said that these events could mean “very unstable times” for North Korea.