South Korea says it failed to reach a breakthrough Wednesday during its first military talks with North Korea in more than three years.
North Korea proposed the talks to discuss two recent incidents in which Pyongyang and Seoul exchanged gunfire across their border.
Last Friday, the two countries traded small arms fire after Pyongyang shot at balloons from the South carrying anti-North propaganda. Earlier last week, North and South Korean naval boats traded warning shots along their disputed Yellow Sea border.
During the five-hour meeting Wednesday, Seoul's defense ministry said it could not agree with the North on what led to the incidents.
Pyongyang accused the South Korean vessels of violating its territory, and called on Seoul to prevent activists from launching more propaganda balloons.
Seoul demanded that North Korean ships stop crossing into what it sees as its territory, and insisted it could not stop private activist groups from launching the leaflets.
The negotiations, held at the Panmunjom border village, were the two rivals' first military talks since February 2011. South Korea says no date for further talks was set.
The increased tensions threaten to unravel high-level talks that were agreed to earlier this month after North Korea unexpectedly sent a senior delegation to the South.
At the proposed talks, which could be held as early as this month, the two sides are expected to discuss the resumption of reunions between families separated by the 1950s Korean War.
There is also speculation that Seoul may consider loosening or lifting sanctions put in place after the fatal sinking of its navy ship, which killed 46 South Korean sailors in 2010.
Recently, Pyongyang has linked lifting the sanctions to progress on inter-Korean relations.