Top aides to the leaders of North and South Korea resumed talks on Sunday after negotiating through the night in a bid to ease tensions involving an exchange of artillery fire that brought the peninsula to the brink of armed conflict.
The meeting at the Panmunjom truce village inside the Demilitarised Zone (DMZ) began on Saturday evening shortly after North Korea's deadline for Seoul to halt anti-Pyongyang propaganda broadcasts or face military action. It broke up before dawn on Sunday.
Even as the talks restarted, the rivals were on high military alert, with the North deploying twice the usual artillery strength at the border and a majority of its submarine fleet - more than 50 vessels - away from bases, the South's defence ministry said.
South Korea, whose military was also on higher alert, said it had no plans to halt the propaganda broadcasts that triggered the latest standoff.
The envoys, shown on TV exchanging handshakes and tight smiles at the start of their meeting, discussed ways to resolve tension and improve ties, South Korea's presidential Blue House said in a brief statement.
"Both sides are under big pressure to get something out of this," said Jeon Young-sun, professor at the Institute of the Humanities for Unification at Konkuk University in Seoul, who said the length of the high-level meeting may be unprecedented.
The talks took place in South Korea's Peace House, just south of Panmunjom's often-photographed sky-blue huts, and the same venue where lower-level talks between the bitter rivals took place in February 2014, without ending in agreement.
The negotiations were interrupted with breaks for both sides to consult with their respective governments, and for snacks, the South's Yonhap News Agency reported.
"North Korea wants to stop broadcasts, while South Korea can't do it without achieving anything back," Jeon said.
Sunday's talks were open-ended, with the South's Blue House expected to announce the results after they conclude.
North Korea and South Korea have remained technically in a state of war since their 1950-53 conflict ended in a truce, not a peace treaty, and inter-Korean relations have been in a deep freeze since the deadly 2010 sinking of a South Korean warship. Pyongyang denied responsibility.
The current tensions began early this month when two South Korean soldiers were wounded by landmines along the border. The North denies laying the mines.
Days later, Seoul began its propaganda broadcasts in random three-hour bursts from 11 banks of loudspeakers, including news reports and K-pop music from the South, resuming a tactic both sides halted in 2004.
The crisis escalated on Thursday when the North fired four shells into the South, according to Seoul, which responded with a barrage of 29 artillery rounds. North Korea declared a "quasi-state of war" in front-line areas and made an ultimatum for Seoul to halt its broadcasts.
That deadline passed on Saturday without any reported incident.
The United Nations, the United States and the North's lone major ally, China, have all called for calm.
The United States, which has 28,500 soldiers based in South Korea, is conducting annual joint military exercises with the South. North Korea regularly condemns the maneuvers as a preparation for war.
South Korean President Park Geun-hye's national security adviser, Kim Kwan-jin, and Unification Minister Hong Yong-pyo met with Hwang Pyong So, the top military aide to the North's leader, Kim Jong Un, and Kim Yang Gon, a veteran North Korean official in inter-Korean affairs, on Saturday, prompting hopes for a breakthrough.
Pyongyang's two negotiators made an unexpected visit to the South last October to attend the closing ceremony of the Asian Games, where they met Kim Kwan-jin. Those talks raised hopes for an improvement in relations, which did not materialize.
North Korea has been hit with UN and U.S. sanctions because of repeated nuclear and missile tests, moves that Pyongyang sees as an attack on its sovereign right to defend itself.