Jang Song Thaek was purged and executed because he met privately with Kim Jong Un's older brother Kim Jong Nam, Professor Kang Myong-do said on Friday.

Professor Kang, who teaches at Kyungmin University and is the son-in-law of former North Korean premier Kang Song San, told YTN that Jang Song Thaek had travelled overseas to give Kim Jong Nam his monthly living expenses in October, a journey that had made Kim Jong Un suspicious that Jang was plotting to replace him.