South Korean President Park Geun-Hye says Seoul will not switch off propaganda broadcasts unless North Korea offers a "clear apology" for what her government sees as a series of provocations.
Park's demand came as the two Koreas were locked in high-level talks on ending a military standoff that has threatened to boil over into armed conflict.
"(North Korea) should make a clear apology... and ensure that there will be no further provocations," she said, blaming Pyongyang for sparking the current military crisis with "provocative activities".
Top-level negotiators from the two Koreas have been engaged in tough talks from Saturday to end the tense standoff along the heavily-fortified border.
But the talks have been clouded by South Korean claims that the North is undermining the negotiating process by moving additional artillery units to the border and deploying dozens of submarines.
The roots of the standoff lie in landmine blasts on the border this month that maimed two South Korean soldiers.
Accusing Pyongyang of laying the mines, Seoul retaliated by switching on giant banks of loudspeakers that had lain silent for more than a decade, blasting high-decibel propaganda messages into North Korea.
The North denied any role in the mine blasts and issued an ultimatum for the South to halt its "psychological warfare" or face attack.