Top-level North and South Korean negotiators talked through the night with no sign of an agreement Monday to exit a high-stakes standoff that has pushed the two rivals to the brink of armed conflict.

After a 10-hour marathon the previous night, the talks passed the 15-hour mark in a second session in the border truce village of Panmunjom, where the 1950-53 Korean War ceasefire was signed.

The second round was clouded by South Korean claims that the North was seeking to undermine 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 earlier 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 and 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.

The negotiations in Panmunjom are being led by South Korean national security adviser Kim Kwan-Jin and his North Korean counterpart Hwang Pyong-So -- a close confidant of leader Kim Jong-Un.

They are the highest-level inter-Korean talks for nearly a year -- a reflection of the seriousness of the situation.