North Korea may be preparing for a visit by international inspectors to its shuttered Punggye-ri nuclear test site, South Korea's Yonhap news agency reported Wednesday, citing the country's spy agency.

"Signs have been detected that North Korea is doing some preparations and intelligence-related activity over a possible visit by outside experts, as it shut down the nuclear test site and demolished some of the missile launching facilities at Dongchang-ri," the National Intelligence Service was quoted as saying by ruling party lawmaker Kim Min-ki.

Pyongyang claimed in May to have dismantled the Punggye-ri site in front of journalists, but did not invite inspectors to confirm the facility's closure. Critics had lambasted the move as merely for show, saying that it could be easily reversed.