North Korea has said it will cut off all inter-Korean communication lines with the South, including a hotline between the two nation's leaders.
The North said this was the first in a series of actions, describing South Korea as "the enemy".
Daily calls, which have been made to a liaison office located in the North Korean border city of Kaesong, will cease from Tuesday.
The two states had set up the office to reduce tensions after talks in 2018.
North and South Korea are technically still at war because no peace agreement was reached when the Korean War ended in 1953.
North Korea "will completely cut off and shut down the liaison line between the authorities of the North and the South, which has been maintained through the North-South joint liaison office... from 12:00 on 9 June 2020," the Korean Central News Agency (KCNA) report said.
Military communication channels would also be cut, North Korea said.
When the liaison office was temporarily closed in January because of Covid-19 restrictions, contact between the two states was maintained by phone.
The two countries made two phone calls a day through the office, at 9am and 5pm. On Monday, the South said that for the first time in 21 months, its morning call had gone unanswered, although contact was made in the afternoon.
"We have reached a conclusion that there is no need to sit face-to-face with the south Korean authorities and there is no issue to discuss with them, as they have only aroused our dismay," KNCA said.
Kim Yo-jong, the North Korean leader's sister, threatened last week to close the office unless South Korea stopped defector groups from sending leaflets into the North.
She said the leaflet campaign was a hostile act that violated the peace agreements made during the 2018 Panmunjom summit between the South's Moon Jae-in and Kim Jong-un.
North Korean defectors occasionally send balloons carrying leaflets critical of the communist region into the North, sometimes with supplies to entice North Koreans to pick them up.
North Koreans can only get news from state-controlled media, and most do not have access to the internet.
Ties between the North and South appeared to improve in 2018, when the leaders of both countries met three times. Such high-level meetings had not taken place in over a decade.
But Pyongyang largely cut off contact with Seoul following the collapse of a summit between Kim and US President Donald Trump in Hanoi last year that left nuclear talks at a standstill.