"(G)iven the pace of the build-up and training, North Korea's upcoming Foundation Day Parade (reportedly to be held on Sept. 9) will probably, at least match but likely surpass the size of the parade held this past February to mark the 70th anniversary of the founding of Korean People's Army," it said in an article posted on its website.

The imagery shows about 500 trucks, which are used to move troops to the training site, a small tent city where troops are housed and fed, six groupings of soldiers moving in parade formation along the facility's roads, and the expansion of storage shelters, according to 38 North.

Preparations for the parade were first observed last month, following a pattern seen in recent parades, it said.

"The number of shelters appears slightly larger than what was used in the February parade, and there are at least 10 pieces of equipment (including several tanks or artillery pieces) in front of their respective shelters," the article said, noting that these shelters have previously been used to house and prepare ballistic missile and unmanned aerial vehicle launchers, tanks, large artillery pieces and other heavy equipment away from view.

"There are no ballistic missile or UAV launchers as of the date of this image," it said.

Recent news reports have speculated that Chinese President Xi Jinping will visit North Korea around the anniversary at the invitation of North Korean leader Kim Jong-un.

It would be Xi's first visit to the communist ally as president and would follow tensions last year over Pyongyang's nuclear and ballistic missile programs.

Meanwhile, Kim traveled to China three times this year to hold talks with Xi and apparently coordinate their steps before and after the North Korean's landmark meetings with South Korean President Moon Jae-in and US President Donald Trump. (Yonhap)