Taken on the morning of Jan. 11, Planet photos also show some 20 dot-shaped groups, apparently troops, lined up at the center of the square, and other photos, taken 30 minutes after them, display some of the groups were moved, the broadcaster said.

On Tuesday, the North abruptly declared Feb. 8 the new founding anniversary of its army, saying it will take "practical" measures to mark the "historic" occasion. April 25 has been honored as the anniversary so far, as it is claimed to be the day when late founder Kim Il-sung, the grandfather of current North Korean leader Kim Jong-un, established the Korean People's Revolutionary Army, in 1934. 

Earlier, a South Korean government official said the mobilization of around 13,000 troops and some 200 pieces of equipment have been detected near the airport, for what appears to be a rehearsal for a military parade.

Notable is that the large-scale military parade is to be conducted one day before the opening of South Korea's Winter Olympic Games, in which North Korean athletes will take part owing to an inter-Korean agreement and an IOC approval. (Yonhap)