As Tokyo keeps watch for another nuclear test by Kim Jong Un's defiant regime, activity has been detected near North Korea's nuclear test site ahead of the anniversary of its Workers' Party on Monday.

According to information published Thursday on the 38 North website, maintained by the U.S.-Korea Institute at the School of Advanced International Studies at Johns Hopkins University, recent satellite imagery of the Punggye-ri nuclear test site from Oct. 1 indicates there is sustained activity at all three tunnel complexes at the site, an indication that there could be another nuclear test almost a month after the country's fifth such test.

"The purpose of this activity is also unclear, although the portal is assumed to be capable of supporting a nuclear test once a decision is made to move forward," said the website.