HUNCHUN, China (AP) — The warning came from Kim Jong Un, the North Korean ruler who sees his isolated nation, just across the border from this busy Chinese trading town, as under siege. The attack, he said, must be stopped.

“We must extend the fight against the enemy’s ideological and cultural infiltration,” Kim said in an October speech at the headquarters of his immensely powerful internal security service. Kim, who became North Korea’s supreme leader after the death of his father a year ago, called upon his vast security network to “ruthlessly crush those hostile elements.”