Seoul, Oct 7 : Military tensions have been continuing between the two Koreas over killing of a South Korean fisheries' official by North Korea, as Pyongyang issued threats over Seoul's search operations without responding to calls for a joint investigation, Seoul's Defence Minister Suh Wook said on Wednesday. On September 22, the 47-year-old fisheries official was fatally shot by the North Korean military while being adrift in North Korean waters, according to the South Korean military. He went missing the previous day while on duty near the Yellow Sea border island of Yeonpyeong, Yonhap news agency reported. "Regarding the incident, North Korea expressed an apology and vowed to take steps to prevent recurrences, but it has not responded to our call for a joint investigation and made threats against our normal search operations under way in our waters," Wook said during a parliamentary audit of the ministry. The communist country warned the South on September 27 not to intrude into its waters in the search for the body of the official. Pyongyang has long disputed the Northern Limit Line (NLL), the de facto inter-Korean maritime boundary, turning the front-line waters into a major flashpoint of the peninsula. Wook made it clear that all responsibilities regarding the incident lie with North Korea, stressing the need for a joint probe, as the North's explanations differ from Seoul's assessment in key parts. The South Korean military said the North is presumed to have incinerated the official's body, but the North claimed that what it set on fire was not his body but a floating material he used. As for concerns raised by a lawmaker over the disclosure of classified military information acquired by South Korean and US assets regarding the incident, Minister Suh said that US Forces Korea (USFK) Commander Gen. Robert Abrams "voiced some concerns" about the excessive exposure. /IANS