Senior military officials from the two Koreas have held talks for the first time in seven years, South Korea's Yonhap news agency reports.
The news agency, citing an unnamed source, said the talks began at 10:00 (01:00GMT) at the truce village of Panmunjom in the Demilitarised Zone.
In recent weeks the two Koreas have exchange limited gun fire across both their land and sea borders.
South Korean ministry officials have not formally confirmed the talks.
Yonhap, citing its parliamentary source, said it was because the North did not want the talks made public.
An opposition lawmaker gave the same information to a party meeting, a statement from his party said.
The talks were widely expected to focus on reducing tensions after two small military incidents across the border that divides the two nations - which remain technically at war.
Last week, gun fire was exchanged after a North Korean patrol ship crossed the disputed western maritime border, South Korea said.
On Friday, there was also an exchange of fire across the land border, something that happens rarely.
South Korea's Yonhap news agency, citing military officials, said the North fired towards balloons carrying propaganda leaflets that had been launched across the border by South Korean activists.
South Korea responded after some shots landed south of the border, its officials said.
The BBC's Stephen Evans in Seoul says the immediate aim of the latest talks was to defuse a dangerous situation, but that there appears to be some desire on both sides to improve relations.
The two sides last held working-level military talks in February 2011 and general-level talks in December 2007, Yonhap said.
In February, Pyongyang and Seoul also had two rounds of high-level meetings in Panmunjom, without providing any details on how the talks went.
Wednesday's unexpected border meeting follows an announcement earlier this month that both countries had agreed to resume high-level talks within weeks.