North Korea has rejected any further talks with South Korea, calling its decision "completely the fault of South Korea's actions".
It issued a statement in response to a speech by South Korea President Moon Jae-in on Thursday.
Meanwhile, early on Friday North Korea test-fired two missiles into the sea off its eastern coast, the South Korean military said.
It is the sixth such test in less than a month.
The two "unidentified projectiles" were fired about 08:00 (23:00 GMT Thursday) and travelled 230km (140 miles) reaching an altitude of 30km (18 miles), South Korea's Joint Chiefs of Staff said.
Six days ago, North Korea fired two short-range ballistic missiles into the Sea of Japan.
The series of tests comes after US President Donald Trump and North Korean leader Kim Jong-un agreed during a meeting in June to restart denuclearisation negotiations.
North Korea has faced international sanctions for its development of nuclear weapons.
What did South Korea say?
In a speech marking Korea's liberation from Japanese rule, President Moon vowed to unite the Korean peninsula by 2045.
Korea divided into two countries at the end of World War Two.
President Moon said the goal of achieving denuclearisation on the Korean peninsula was at its "most critical juncture", as talks between North and South appear deadlocked.
"A new Korean peninsula, one that will bring peace and prosperity to itself, east Asia and the world, awaits us," he said in the televised speech.
What has the North Korea reaction been?
In a statement, the North questioned the meaning of dialogue when "even at this moment, South Korea continues its joint military exercise and to speak of a peaceful economy or a peaceful regime. It has no right to do so."
In an extended attack on President Moon, the statement continued: "We even question if his thought process is sound when he mentions 'talks' between North and South while playing out war scenarios that plan to destroy most of our armies in 90 days.
"He truly is a shameless man."
North Korea has expressed anger over the US-South Korean military drills currently taking place, stating that they violate agreements reached with US President Donald Trump and President Moon.
It has previously described them as a "rehearsal for war".
In a recent letter to Mr Trump, North Korea's leader Kim Jong-un is said to have complained "about the ridiculous and expensive" military exercises.
The deadlock in denuclearisation talks is entirely the fault of South Korea's decision to hold the drills, the North's reunification spokesman said.
North Korea fires missiles as South begins joint drill with US.
"We have no more words to talk with South Korean officials," the official said in a statement carried by the state-run Korean Central News Agency.
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