Air Koryo may have cut the number of flights from three to two due to reduced tourist demand over the winter and the need to save on aviation fuel, which is subject to an export ban under UN sanctions imposed over North Korea's nuclear and missile programmes.

The airline will continue a twice-weekly flight schedule until the end of February, the official said. Up to December, Air Koryo had served the route on Tuesdays, Thursdays and Saturdays, but has now discontinued the Thursday flights.

The carrier suspended flights connecting Pyongyang and China's Shenyang in late December, but plans to resume the service in mid-January.

Air China also serves the Pyongyang-Beijing route, but the Chinese airline suspended flights in late November due to a lack of demand.

It is expected to resume the service, but no earlier than March.

An official in the company's Beijing-based press office, who did not give his full name, said in November that flights were suspended because "business was not good".

Air China flights to Pyongyang, which have traditionally operated on Mondays, Wednesdays and Fridays, began in 2008, but have frequently been cancelled because of unspecified problems, state media has said.

The company cancelled some flights in April, but later said that it would increase their number in May.

The United States has urged China to do more to press North Korea to stop what the United States sees as belligerent defiance of UN resolutions.

Tourism to North Korea is not penalised by United Nations sanctions and is one of the few remaining ways that North Korea earns hard currency.

The Korea Maritime Institute, a South Korean think tank, estimates that tourism generates about US$44 million in annual revenue for North Korea.

China has never publicly announced a ban on Chinese tourists visiting Pyongyang and strongly opposes sanctions imposed by only one nation such as the US, which it says undermines UN unity.

China's trade with North Korea has already fallen to its lowest in months. Beijing has repeatedly said it is rigorously enforcing UN resolutions aimed at reining in Pyongyang's missile and nuclear programmes.