North Korea has threatened to block South Korean access to a joint industrial zone on the border between the two countries, Yonhap news agency said, quoting a North Korean military commander. The move comes amid rising tensions between Pyongyang and Seoul following the sinking of a South Korean warship in the Yellow Sea in March, which is blamed on North Korea. "In response to the intention of military puppets to resume psychological provocations against our republic, we will react ruthlessly along the entire front," the North Korean military official said. The Kaesong Industrial Park located just ten kilometers (six miles) to the north of the Korean Demilitarized Zone, hosts plants and factories owned by a total of 121 South Korean companies. Some 700 South Korean citizens work in the industrial park. On Wednesday, North Korea expelled eight South Korean government officials from the industrial zone in a sign of protest against Seoul's accusations that the North was responsible for the death of 46 South Korean sailors on board the sunken Cheonan corvette. North Korea said on Thursday that it is withdrawing all its military safeguards in its relations with the South and scrapping their agreement aimed at preventing clashes off the west coast, Yonhap said. The 1,200-ton warship sank near the disputed Northern Limit Line in the Yellow Sea on March 26. An international investigation showed that the ship was destroyed by a torpedo launched from a North Korean submarine. The international community has condemned the North of jeopardizing peace on the Korean Peninsula. UN Secretary General Ban Ki-moon has called for the Security Council to take prompt actions against Pyongyang. North Korea has called the results of the investigation "a fabrication," and warned Seoul of a stern response if the South retaliated with new sanctions against Pyongyang. The two countries remain technically at war as their 1950-1953 conflict ended only in an armistice. Philip Crowley, the assistant secretary to the U.S. Department of State, said the United States China, Russia, Japan, and South Korea, who are involved in six-party talks on North Korea's nuclear program, should "send a very clear and compelling message" to the North Korean authorities to "choose a different path." On Monday, South Korea froze economic relations and maritime communications with its northern neighbor. The decision is yet another blow for the North's economy already damaged by past UN sanctions intended to force Pyongyang to quit its nuclear program.