"Firstly, all the agreed points concerning the issue of putting an end to the political and military confrontation between the North and the South will be nullified," Yonhap quoted the North's Committee for the Peaceful Reunification of Korea as saying in a statement.
"Secondly, the Basic Agreement on reconciliation and the points on the military boundary line in the West Sea [Yellow Sea] stipulated in its appendix will be nullified," the statement said.
The two Koreas have a dispute over a maritime border in the Yellow Sea - the site of bloody clashes between the two countries' navies in 1999 and 2002.
The western sea border, called the Northern Limit Line, was unilaterally drawn by the U.S.-led United Nations Command at the end of the 1950-53 war, and North Korea insists it should be redrawn farther south.
The reclusive communist state also warned that a new war could break out on the Korean peninsula if South Korea's conservative government continued aggravating tensions.
The two countries are still technically at war as their 1950-53 conflict ended in a truce rather than a peace treaty.
Relations between Seoul and the communist North have deteriorated since South Korean President Lee Myung-bak took office in February 2008.
After coming to power last February, Lee said he would review agreements reached at the 2000 and 2007 inter-Korean summits, and demand more in return from the North for the economic support provided by Seoul.
Relations between the two sides were dealt a further blow last month, when the North tightened controls on the heavily fortified border, and expelled some of the South Koreans working at the country's Kaesong industrial park.
North Korea tested a nuclear bomb in 2006, but later signed a deal with the U.S., South Korea, Japan, Russia and China pledging to dismantle its nuclear program in return for aid. However, the process has seen no progress since August, and December talks in Beijing failed to break the deadlock.
