According to Washington-based think tank 38 North, satellite images allegedly spotted a train belonging to North Korean leader Kim Jong Un at the Wonsan resort area in the east of the country on 21 and 23 April.
The train, which is about 250 metres long, was partially covered by the roof at the station reserved for use by Kim and his family, the think tank said. The train was not present on 15 April but was spotted on 21 and 23 April, it added.
The report emphasized that the presence of the train does not mean that Kim Jong Un was there, neither does it says anything about his health.
The Wonsan complex is believed to be Kim's residence outside Pyongyang.
Earlier this month, some media speculated on the North Korean leader's health after he missed the celebration of his grandfather's birthday. Reuters reported, citing unnamed sources that China had sent medical experts to North Korea to provide consultation for Kim Jong Un. CNN, for its part, reported, quoting an anonymous US official, that the North Korean leader had allegedly undergone surgery.
Although the North Korean leader has remained absent from state media coverage, Pyongyang has not commented on his health condition.