North Korea's Kang Kon Military Academy, which trains the country's top officers, has hung up signs with a quote from nation founder Kim Il-sung that China is a "turncoat and our enemy."
Kim made the remark during a visit to the academy in 1992, angered by Beijing's decision to establish diplomatic relations with South Korea.
The former leader then instructed school officials to hang signs bearing his remark on the walls of the school, which remained there until 1995. They reappeared briefly in 2009 after the North conducted its second nuclear test.
North Korean leader Kim Jong-un ordered the signs displayed again at the academy after China joined UN Security Council sanctions last year over the North's long-range missiles and third nuclear test.
Sources say the signs also urge soldiers to take a "proper view" of China and to incite revolution on the Korean Peninsula without outside help.
The signs are reportedly also displayed at training schools for high-ranking Workers Party officials.
A source said, "The position of the North Korean regime is to use China, but not trust it."