President Trump on Thursday said he was "very disappointed" to learn that China had reportedly been caught illegally selling oil to North Korea, violating international sanctions imposed in September that indefinitely barred the Kim regime from importing natural gas and crude oil.

"Caught RED HANDED – very disappointed that China is allowing oil to go into North Korea," Trump wrote in a tweet. "There will never be a friendly solution to the North Korea problem if this continues to happen!"

The president's tweet comes after photos emerged this week that appeared to show Chinese vessels trading oil with North Korean boats in the West Sea. The satellite images were first published by a South Korean media outlet, which claimed that China had sold oil to Pyongyang around 30 times since October.

Chinese officials denied participating in any sanction-breaking oil sales on Thursday.

"The situation you have mentioned absolutely does not exist," Defense Ministry spokesman Ren Guoqiang told reporters at a briefing.

Multiple rounds of sanctions have been leveled against North Korea by the U.N. Security Council in order to pressure its leader Kim Jong Un into abandoning his nuclear weapons program.

The UNSC imposed an oil embargo on the hermit kingdom in September, two months before Trump visited Beijing, where he engaged in bilateral talks about North Korea with Chinese President Xi Jinping.