Seoul, Sept. 28 -- South Korea on Sunday voiced "strong regret" over Ukraine's denial of a "nondisclosure agreement concerning" the transfer of two North Korean prisoners of war (POWs) to South Korea, according to Yonhap News Agency.

The South Korean presidential office said it "expresses strong regret over Ukraine's unilateral disclosure (of the transfer) and its subsequent false announcement that there had not been a nondisclosure agreement," senior presidential secretary for public relations Seong Ghi-hong said.

Seong added that South Korea was considering additional measures if necessary.

Yonhap reported Ukrainian media coverage that a Ukrainian presidential source denied the existence of a confidentiality agreement with Seoul.

So...