(QHA) -

The once-powerful uncle of North Korean leader Kim Jong-un has been executed after being purged for "acts of treachery", state media say, BBC informs.

Chang Song-thaek was dramatically removed from a special party session by armed guards earlier this week.

It was the biggest upheaval since Mr Kim succeeded his father two years ago.

State news agency KCNA said Mr Chang had admitted at a military trial on Thursday to attempting to overthrow the state, and was executed immediately.

Mr Chang, who is thought to have mentored his nephew during the leadership transition from Kim Jong-il to his son Kim Jong-un in 2011, was "worse than a dog", said the agency.

He had admitted abusing his positions of responsibility to form a faction against the state and to harbouring his own political ambitions, it said in a lengthy and detailed report.

In the US, the White House said it could not independently verify the reports but had "no reason to doubt" them.

"If confirmed, this is another example of the extreme brutality of the North Korean regime. We are following developments in North Korea closely and consulting with our allies and partners in the region," it said in a statement.