Drivers in North Korea's capital Pyongyang were scrambling to fill up their tanks as gas stations began limiting services or even closing down amid concerns of a spreading shortage.
Signs outside some stations in the North Korean capital said sales were being restricted to diplomats or vehicles used by international organisations, while others were closed or turning away local residents.
The cause of the restrictions or how long they might last were not immediately known. But North Korea depends heavily on China's fuel supply and Beijing has reportedly been tightening its enforcement of international sanctions, aiming to end Pyongyang's 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 did not give a clear response on fuel restriction.
"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."
Kim Dong-jil, director of the Center for Korean Peninsula Studies of Peking University, said he had not heard of new restrictions on fuel to pressure Pyongyang, but said they are considered to be an option.
China's Ministry of Commerce had no immediate comment.
Increase in gasoline prices
According to a sign outside a station where ordinary North Korean vehicles were being turned away, the restrictions took effect on Wednesday and prices appeared to be rising significantly.
Gasoline was selling at $1.25 per kilogram at one station, up from the previous 70-80 cents.
Supply is controlled by the state and the military, state ministries and priority projects have the best access.
"Ready to respond"
US and South Korean officials have been saying for weeks that the North could soon stage another nuclear test in violation of United Nations sanctions, something the United States, China and others have warned against. It is unclear whether the restriction on fuel supply is a move by Beijing to prevent that from happening.
US President Donald Trump has also reiterated in recent weeks that he would prevent North Korea from being able to hit the United States with a nuclear missile.
And on Saturday North Korean state-run television KRT said the country's military was ready to respond to American aggression, quoting its foreign ministry statement.
Tensions have risen sharply in recent months after North Korea conducted two nuclear weapons tests last year and carried out a steady stream of ballistic missile tests.
New satellite imagery analysed by 38 North, a Washington-based North Korea monitoring project, found some activity under way at North Korea's Punggye-ri nuclear test site.
But they said it was unclear whether the site was in a "tactical pause" ahead of another test or was carrying out normal operations.
As North Korea will mark the 85th anniversary of the foundation of its Korean People's Army on Tuesday, South Korean acting President Hwang Kyo-ahn has told top officials that given the April 25 anniversary, there were concerns that North Korea "can make another provocation again at any time."