Amid rising speculation over the health of North Korean leader Kim Jong-un, the North's state media reported that Kim expressed gratitude to workers building a tourist zone in the east coast region of Wonsan.

The Korean Central Broadcasting Station and Rodong Sinmun on Monday said Kim sent his appreciation to the workers who devoted themselves to constructing the Wonsan-Kalma tourist zone, one of Kim's pet projects.

The latest report comes after 38 North, a U.S.-based think tank, revealed on Saturday satellite imagery of what appeared to be Kim's special train parked at a station in his Wonsan compound since at least April 21.

Moon Chung-in, a special security adviser to President Moon Jae-in, told Fox News on Sunday that Kim has been staying in the area since April 13, and that he is "alive and well."

Earlier, CNN and some other media outlets reported on Kim's possible ill health following surgery, after he missed a key annual ceremony on April 15 commemorating the birth of his grandfather and the regime's late founder Kim Il-sung.

Kim Jong-un was last seen in state media on April 11, presiding over a political bureau meeting of the ruling Workers' Party.