North Korea has withdrawn from the inter-Korean liaison office which was opened amidst warming of ties last year to facilitate talks with the South.
On Friday, Seoul said that it was contacted and informed that the North's staff would be leaving later in the day.
It has expressed its regret at the decision and is urging staff from the North to return as soon as possible.
The pullout follows a failed summit between the US and North Korean leaders in Hanoi last month.
The liaison office, located in the North Korean border city of Kaesong, had allowed officials from North and South Korea to communicate on a regular basis for the first time since the Korean War. It is meant to be staffed by up to 20 people from each side.
At the time, Seoul's Unification Minister said it would allow for direct discussion of any issues "24 hours, 365 days".