The move is to bolster young leader Kim Jong Un's grip on power after his uncle's execution.
He is accused of attempting to overthrow the government of his young nephew.
Analysts say Jang Song Thaek was seen as a threat to Kim’s power.
U.S. asks Pyongyang to release another American citizen in North Korean custody.
The purge of Jang Song Thaek came more quickly than expected, a North Korea expert says.
The products are refused on suspicion of originating in the South.
Jang Song Thaek may have been eased out in a power struggle with the top political operative for the army.