Jang Song-Thaek, 67, along with five close aides, was stripped naked and thrown into a cage of hounds which had been starved for three days, according to new details emerging from China.
The pack of animals spent more than an hour mauling the group in a punishment called quan jue, or execution by dogs, a report in Chinese newspaper Wen Wei Po said.
The report added the entire process was supervised by Kim, 30, along with 300 senior officials.
The tyrannical leader of the communist state had accused his uncle - once seen as North Koreas second most powerful man - of treason and corruption and described him as scum and factionalist filth during his recent New Year message.
Unlike previous executions of political prisoners, which were carried out by firing squads with machine guns, this extraordinary sentence seems to have been specially reserved for the most hated in North Korean society.
The leader appeared on state television for the speech and analysts say the words reflect his feelings towards aides of his uncle, Jang Song-Thaek, and other family members who are believed to have been sent to labour camps.
His statement on state TV was the first time he had publicly criticised his uncle, who was executed on December 12 after he was accused of treason, corruption, following the ways of the hated West, and being a womaniser.
It was also claimed he pursued a decadent capitalist lifestyle, squandering 3million in 2009, some in a foreign casino.
Jang had mentored Kim as he took the reins of power in the highly secretive country. And experts believe the execution is a bid by Kim to assert his authority and independence as leader.
The pack of animals spent more than an hour mauling the group in a punishment called quan jue, or execution by dogs. The entire process was supervised by Kim Jong-un himself.