North Korean trade with China is springing back to life, easing pressure on Kim Jong Un whose economy has been battered by sanctions and border closures owing to the coronavirus pandemic.

At least 52 vessels that appear to be linked to Pyongyang were active in waters around North Korea and China in April and May, up from single digits observed for weeks at a time last year, according to data analysed by NK Pro, a North Korea-focused information service.

The latest data, which are based on automatic identification system records, also showed an increase in the number of North Korea-flagged tankers operating in the area, suggesting a resurgence in Chinese fuel transfers or sales to Pyongyang.

The increased shipping activity follows warnings of worsening food shortages and economic crisis in North Korea. Kim has in the past year made rare admissions of failure in North Korea’s development.

Analysts said Beijing was probably maintaining a years-long policy of supporting stability in Pyongyang through deliveries of food, fertiliser and fuel.

Go Myong-hyun, an expert on the North Korean economy at the Asan Institute for Policy Studies in Seoul, said North Korea’s “drastically lower” import levels last year also stemmed from a steep decline in foreign currency reserves after the pandemic caused trade levels to plummet.

“They need some time to make up for the shortfall in exports before their imports return to the level that we used to see before,” Go said.

Shipments between North Korea and China do not necessarily breach the US-led sanctions designed to hamper North Korea’s nuclear weapons programme.

However, throughout 2020 illicit fuel deliveries to North Korea continued via ship-to-ship transfers and “elaborate subterfuge”, according to a UN report.

The questions over Chinese support for North Korea and Pyongyang’s sanctions-busting activity have risen just weeks after Washington completed a policy review of North Korea. The US has said it was open to diplomatic contact and a resumption of frozen nuclear talks.

Many North Korea-focused analysts believe President Joe Biden is attempting to avoid dealing with the security threats posed by the Kim regime’s nuclear weapons arsenal while his administration tackles more urgent foreign policy priorities, such as China.

Go said the Biden administration appeared to be downplaying sanctions enforcement as part of a broader aim to keep relations with Pyongyang stable, rather than provoke a return to missile or nuclear tests.

“The Biden administration doesn’t want to provide any pretext to North Korea to speed up their provocation cycle,” he said.

International aid organisations warn that North Korea’s 25m people face a humanitarian crisis with aid shipments cut off because of fears of coronavirus transmission.

Additional reporting by Sherry Fei Ju in Beijing