Car users in Pyongyang are scrambling to fill up their tanks as gas stations begin limiting services or even closing amid concerns of a spreading shortage.

A sign outside one station in the North Korean capital said on Friday that sales were being restricted to diplomats or vehicles used by international organisations, while others were closed or turning away local residents. Lines at other stations were much longer than usual and prices appeared to be rising significantly.

The cause of the restrictions or how long they might last was not immediately known.

North Korea relies heavily on China for its fuel supply and Beijing has reportedly been tightening its enforcement of international sanctions aimed at getting Pyongyang to abandon its development of nuclear weapons and long-range missiles.

The issue was raised at a regular Chinese foreign ministry news conference in Beijing on Friday after a Chinese media outlet, Global Times, reported gas stations were restricting service and charging higher prices.

But spokesman Lu Kang gave an ambiguous response when asked if China was restricting fuel deliveries.

"As for what kind of policy China is taking, I think you should listen to the authoritative remarks or statements of the Chinese government," he said, without elaborating on what those remarks or statements are. "For the remarks made by certain people or circulated online, it is up to you if you want to take them as references."