North Korea's Supreme Leader Kim Jong-un has reportedly died following a 'botched' heart operation earlier this month.

The 36-year-old's health has been the subject of much speculation all month after he missed the Day of the Sun festival, which honours his late grandfather's birthday, on April 15.

According to Qing Feng, vice-president of the Hong Kong news channel HKSTV, a "very solid source" has informed her that the leader has passed away in hospital.

Reports from Japan earlier today suggested that Kim Jong-un was in a "vegetative state" and effectively braindead after the operation, which is thought to have happened on April 12.

Other reports - also unconfirmed - have suggested that his heart surgery went wrong because "the surgeon's hands were shaking so badly".

North Korea is a notoriously secretive country, particularly with matters concerning its officials, and there has yet to be any official word on Kim's condition.

Kim's younger sister Kim Yo-jong is the favourite to take over as Supreme Leader in the event of his death.