More than 430 South Koreans have crossed into North Korea and met with relatives for the first time since they were separated by the Korean War more than half a century ago.
The divided family members - mostly aged in their 80s - are meeting for three days in North Korea's Diamond Mountain resort, South Korea's Unification Ministry said.
More than 20,800 family members have had brief reunions in face-to-face meetings or by video since a landmark inter-Korean summit in 2000.
There are no postal, telephone or email exchanges between ordinary citizens across the heavily fortified border, so such reunions are emotional for Koreans and most participants are elderly people eager to see loved ones before they die.
Saturday's reunions - the first in more than a year - came a day after North Korea fired two rounds at a South Korean guard post in the Demilitarised Zone and South Korean troops immediately fired back. No injuries were reported.
The shooting came just hours after North Korea threatened to retaliate for South Korea's refusal last week to hold military talks.
The US-led UN Command - which oversees the armistice that ended the 1950-53 Korean War - is considering launching an investigation into the shooting incident, a command official said.
The exchange lasted just a few minutes but highlighted the security challenges South Korea faces as it prepares to host next month's Group of 20 summit in Seoul, just 30 miles from the border.
The South, a major global economy with one of the highest standards of living in the world, is still technically at war with the North because their conflict ended in a truce, not a peace treaty. Tens of thousands of troops stand guard on both sides of the border dividing the Koreas.
Communist North Korea has a track record of provocations against South Korea at times of internal change, external pressure or when world attention is focused on Seoul.