SEOUL (AFP) - Less than two weeks after securing a rare deal to improve relations, North and South Korea are already back on more familiar territory, trading accusations of insult and insincerity.

Previous agreements have been scuppered by similar verbal disputes, which can easily escalate into something more serious.

The North's annoyance over comments made by South Korean President Park Geun Hye in Beijing this week drew a sharp response from Seoul on Friday.

"It is regrettable that North Korea is lambasting remarks made by our president... and threatening to scuttle the inter-Korean agreement," the South's Unification Ministry spokesman Jeong Joon Hee told journalists.

Jeong urged the North to cooperate and "sincerely implement" the August 25 agreement that allowed both sides to step back from the brink of an armed conflict.

As well as addressing the issues that led to a tense military standoff, the agreement committed both sides to beginning official talks and organising a reunion for families separated by the 1950-53 Korean War.

But the North took exception to Park's remarks in Beijing where she thanked China for its "constructive role" in resolving the crisis - a third-party credit Pyongyang took as a "serious insult".

"The South Korean authorities are repeatedly uttering wild remarks," said a spokesman for the North's Committee for Peaceful Reunification of Korea.

"If the South Korean authorities persist in... peddling the internal issues of the nation abroad, North-South relations will slip back into the evil cycle of confrontation," the spokesman said.

He also bristled at Park's suggesting that North Korean "provocation" was behind the recent standoff.

Under the terms of the August agreement, Seoul switched off loudspeakers blasting propaganda messages across the border after the North expressed regret over recent mine blasts that maimed two South Korean soldiers.

The South interpreted the regret as an "apology" but the North's powerful National Defence Commission has since stressed that it was meant only as an expression of sympathy.