North Korean leader Kim Jong-un is said to be suffering from gout, a hereditary disease which he seems to have inherited from his father and grandfather.

The ruling North Korean leader, who is believed to be his early thirties, has not been seen in public for more than three weeks.

He also skipped the regular session at the Supreme People's Assembly in Pyongyang on Thursday 25 September amid increasing speculation he is severely ill.

"Kim Jong-un is suffering from gout, which is why he is limping on both legs. I understand that he is suffering from gout along with hyperuricemia, hyperlipidemia, obesity, diabetes and high blood pressure," a source familiar with North Korean affairs told South Korea's Yonhap news agency.

The source went on to say gout, which is often caused by obesity and disorderly eating, runs in Kim's family as both his predecessors, father Kim Jong-il and grandfather Kim Il-Sung, suffered from the disease.

Photos from state media have showed that after his father died in 2011, Kim had put on a lot of weight after he came into power. Meanwhile, a pre-recorded documentary broadcast on Thursday showed Kim struggling while he was walking.

"The wealth and prosperity of our socialism is thanks to the painstaking efforts of our marshal, who keeps lighting the path for the people, like the flicker of a flame, despite suffering discomfort," stated a voice-over in the documentary, as reported in The Guardian.

There is also growing speculation North Korean doctors are visiting some parts of Europe or European doctors visiting the reclusive nation, in order to arrange treatment for the ailing leader.

Kim was last seen on 3 September during a concert flanked by his wife. He was walking with a limp during the performance.