Air China Ltd will increase its flights between Beijing and the North Korean capital, Pyongyang, from early May, after it cancelled some flights this month because of what it said was weak demand.

China's national airline said on April 14 some flights would be temporarily cut "based on the situation of ticket sales", but it denied a report by state broadcaster CCTV that its flights to Pyongyang would be suspended indefinitely.

The CCTV report stirred speculation the scaling back of flights was in response to tension between North Korea and the United States over North Korea's nuclear weapon and missile development.

China is North Korea's sole major ally but disapproves of the North's weapons programmes and has supported U.N. sanctions against it.

Searches on Air China's website on Tuesday showed the carrier will have one flight a week, on Fridays, for the first two weeks of May, and after that, two flights a week, on Monday and Friday.

Searches showed no flight scheduled for Friday this week.

Reuters could not immediately reach Air China for comment.

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.

Following repeated missile tests that drew international criticism, China banned all imports of North Korean coal on Feb. 26, cutting off its most important export. Chinese media have raised the possibility of cutting oil shipments to North Korea, if it were to conduct another nuclear test.

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