The Bank of China has closed the account of a North Korean bank which is being targeted by the United States.
The BBC reports the Bank gave no reason for halting transactions at the North Korean Foreign Trade Bank.
Bank of China is the country's biggest foreign exchange bank.
The closure is the first publicly announced step taken by a Chinese agency to curb its dealings with North Korea which is under international pressure over its nuclear and ballistic missile programmes.
China is North Korea's traditional ally and its biggest trading partner. It is unclear how much of their $US6 billion in annual bilateral trade goes through the Foreign Trade Bank.
China has become increasingly frustrated with North Korea in recent months. It agreed to new UN sanctions after Pyongyang conducted its third nuclear test in February.