The Democratic People's Republic of Korea (DPRK)'s explanation on unannounced dam discharge was not enough, South Korea's Unification Ministry said on Monday.

South Korean rescue workers carry the body of a flood victim at the Imjin River near the Demilitarized Zone which separates the two Koreas in Yeoncheon, Sep.7, 2009. South Korean Prime Minister Han Seung-soo on Monday expressed regrets about the DPRK's unannounced discharge of water from a dam, which may have caused the disappearance of six South Koreans. [Xinhua/AFP Photo]

In response to Seoul's protest on deadly flood that left three South Koreans dead and three others missing, the DPRK told the South that a sudden increase of water in its border dam prompted a massive discharge, South Korea's Yonhap News Agency quoted the ministry as saying.

Pyongyang said in a faxed letter that they found that "the water was discharged on emergency as it reached high levels," and promised to issue alerts in the future to prevent similar accident from happening, the ministry said.

However, South Korea expressed deep regret in a statement after receiving Pyongyang's response, saying that the DPRK's notice "is not sufficient enough to convince us and it had no mention of the loss of human lives on our side."

Rescue workers search for missing people in a vehicle swept away by sudden rising water, partially submerged in the Imjin river near the demilitarized zone separating the two Koreas in Yeoncheon, Sep.7, 2009. South Korean Prime Minister Han Seung-soo on Monday expressed regrets about the DPRK's unannounced discharge of water from a dam, which may have caused the disappearance of six South Koreans. [Xinhua/AFP Photo]

Six South Korean campers, including one child, went missing Sunday morning while camping at a riverside site in Yeoncheon, downstream of the Imjin River, which originates in the DPRK.

"They were apparently swept away by a huge wave released by a dam in the DPRK," South Korean police said, adding that the discharge of water caused a sudden surge in the river level from 2.3 meters to 4.96 meters.

Three people were found dead Monday morning, while the others were still missing, police said.

Seoul lodged a complaint earlier the day over the tragedy.

(Xinhua News Agency September 8, 2009)