The images come a day after senior US envoy Glyn Davies warned the North that a nuclear test would unify the world in seeking swift, tough punishment.
Both of North Korea’s previous nuclear tests, in 2006 and 2009, followed rocket launches.
North Korea, meanwhile, shot back in a statement Tuesday, saying it will keep developing its nuclear program if the United States continues to “stifle” the country.
A Foreign Ministry spokesman made no direct threat of a nuclear test, but said North Korea feels compelled to strengthen its “nuclear deterrent” in the face of US hostility. However, the spokesman also said North Korea is open to dialogue to resolve the standoff.
Koh Yu-hwan, a North Korea professor at Seoul’s Dongguk University, said the North’s message is that “the US should come to the dialogue table (with North Korea) if it wants to stop its nuclear test.”