South Korea on Friday expressed doubts about the sincerity of the Democratic People's Republic of Korea (DPRK) towards the recent peace call, citing past provocations. Unification Ministry spokesman Kim Eui-do said in an official statement responding to the DPRK's open letter sent that Seoul still had doubts about the DPRK's sincerity towards its recent peace overture as there were several cases where Pyongyang provoked after peace calls in the past. The open letter claimed that the DPRK's "important proposal" was not a "camouflaged" peace offensive, Kim said, noting that the South Korean government was anticipating the claim would be real. One of the several cases, which Seoul cited as the cause of its suspicion, was the third nuclear test conducted by the DPRK in February last year. Less than two months after stressing the importance of improved inter-Korean relations in its New Year's message, Pyongyang carried out its nuclear test, while nullifying the armistice agreement, posing a threat of nuclear strike and shutting down the Kaesong industrial complex, according to the statement. Kim said that whether it is a disguised peace offensive could not be recognized at one time with words, urging the DPRK to prove its sincerity with action from now on. The DPRK's National Defense Commission (NDC) sent an open letter Thursday under a special order from top leader Kim Jong Un, according to a report carried on Friday by the official KCNA news agency. The letter urged South Korea to stop all hostile military acts, the biggest hurdle stoking distrust and confrontation, stressing that the DPRK's initial peace call was not "camouflaged." On Jan. 16, the NDC made a three-point "important proposal," saying that inter-Korean relations could thaw if the two sides make concerted efforts to implement the proposal starting from Jan. 30, the Lunar New Year holiday. The commission especially urged Seoul to cancel its annual military drills with the United States scheduled for late February to April, but South Korea rejected the call, saying the exercise is defensive in nature. The letter said that Pyongyang's claim was to stop the rehearsal for such northward invasion, noting that if Seoul and Washington want to push ahead with it, they could do that in the U. S. territory or any silent place awayfrom the Korean Peninsula. It also said that the DPRK decided to take actions to stop all hostile military acts on the ground as well as in the air and sea of the frontline, including the disputed five islands off the West Sea.