North Korea has test-fired more missiles into the sea and cancelled proposed peace talks with the South.
Pyongyang has also described its neighbour's president Moon Jae-In as an "impudent guy" because of joint military drills with the US.
It is thought North Korea's recent weapons tests are also a response to stalled nuclear talks with the US.
According to South Korea's military, two short-range projectile were fired by North Korea into the sea on Friday morning local time.
A spokesperson said they appeared to be "short-range ballistic missiles", but more analysis was needed to confirm details.
It's the sixth such launch in the past three weeks.
Meanwhile, North Korea sharply criticised President Moon - accusing him of being "reckless".
It comes in the wake of a televised address by the South Korean president in which he pledged to unite the two countries by 2045.
He insisted the "momentum for dialogue remains unshaken" despite recent "worrying actions" taken by the North.
The speech marked the anniversary of liberation of the peninsula from the 1910-1945 Japanese colonisation.
State-run media in the North claimed talks between the two sides have reached a deadlock, blaming the regular military drills between the US and South.
Such military exercises are regular occurrences, but are strongly opposed by Pyongyang.
North Korean state media quoted a spokesperson as saying: "We have nothing to talk about any more with the South Korean authorities nor do we have any [plans] to sit with them again."
Relations between the North and South have appeared to improve in recent years, with President Moon meeting Kim Jong-Un on a number of occasions.
North Korea and the US have also made strides in improving relations, although nuclear talks have repeatedly stalled despite several high-profile meetings between Donald Trump and Kim Jong-Un.
