U.S. reconnaissance satellites have spotted Chinese ships selling oil to North Korean vessels on the West Sea around 30 times since October.
According to South Korean government sources, the satellites have pictured large Chinese and North Korean ships illegally trading in oil in a part of the West Sea closer to China than South Korea.
The satellite pictures even show the names of the ships. A government source said, "We need to focus on the fact that the illicit trade started after a UN Security Council resolution in September drastically capped North Korea's imports of refined petroleum products."
The U.S. Treasury Department placed six North Korean shipping and trading companies and 20 of their ships on sanctions list on Nov. 21, when it published spy satellite images taken on Oct. 19 showing a ship named Ryesonggang 1 connected to a Chinese vessel.
The department noted that the two ships appeared to be illegally trading in oil from ship to ship to bypass sanctions.
Ship-to-ship trade with North Korea on the high seas is forbidden in UNSC Resolution 2375 adopted in September, but such violations are nearly impossible to detect unless China aggressively cracks down on smuggling.
The problem is that any oil embargo imposed on the North in the event of further provocations will probably be futile as long as illegal smuggling continues.
It is uncertain whether the Chinese government is deliberately looking the other way, but it seems unlikely that it is unaware given the sheer volume.