Satellite imagery showing recent movements of luxury boats often used by North Korean leader Kim Jong-un and his entourage near Wonsan provide further indications he has been at the coastal resort, according to experts who monitor the reclusive regime.

Speculation about Kim’s health and location erupted after his unprecedented absence from April 15 celebrations to mark the birthday of his late grandfather and North Korea's founder, Kim Il Sung.

On Tuesday, North Korea-monitoring website NK PRO reported commercial satellite imagery showed boats often used by Kim had made movements in patterns that suggested he or his entourage may be in the Wonsan area.

That followed a report last week by a US-based North Korea monitoring project, 38 North, which reported satellite images showed what was believed to be Kim’s personal train was parked at a station reserved for his use at the villa in Wonsan.

Officials in South Korea and the US say it is plausible Kim may be staying there, possibly to avoid exposure to the new coronavirus, and have expressed scepticism of media reports he had some kind of serious illness.

They caution, however, that Kim’s health and location are closely guarded secrets and reliable information is difficult to obtain in North Korea.

he last time official media in North Korea reported on Kim’s whereabouts was when he presided over a meeting on April 11, but there have been near-daily reports of him sending letters and diplomatic messages.

Kim’s seaside compound in Wonsan, on the country's east coast, is dotted with guest villas and serviced by a private beach, basketball court, and private train station, according to experts and satellite imagery. An airstrip was bulldozed last year to build a horse riding track, while a boathouse nearby shelters Kim’s Princess 95 luxury yacht, valued at around $7 million in 2013.

“It’s one of his favourite houses,” said Michael Madden, a North Korea leadership expert at the US-based Stimson Center, who has compared Kim’s affinity for Wonsan to US President Donald Trump’s Mar-a-Lago in Florida.