South Korea on Thursday slammed North Korea for issuing a "rude" questionnaire that urged President Park Geun-Hye to choose between peace and confrontation.
The South's Unification Ministry said instability was growing in and around the Korean peninsula because of Pyongyang's "unethical and irrational" attitude.
"North Korea must bear in mind that our government and the international community are watching and assessing how it behaves," the ministry said in a statement.
The statement came a day after a North Korean state body in charge of inter-Korean affairs issued an open questionnaire, addressed to the South's president, through its official news agency.
"Confidence or confrontation?" asked the questionnaire from the secretariat of the North's Committee for the Peaceful Reunification of Korea.
The committee described Park as a US "stooge" who has strained cross-border relations with a policy of "fierce confrontation" with North Korea.
"Park Geun-Hye must not forget the tragedy of her father who ended up in a disgraceful death after losing public confidence. Now it's time to make a final, right choice," it said.
'Ill-mannered'
Park's father, Park Chung-Hee, a former military strongman, seized power through a coup in 1960 and was assassinated in 1979 by his spy chief.
The unification ministry said the North's questionnaire was "ill-mannered".
"We believe such a rude questionnaire from North Korea might be an attempt to distract attention from its internal confusion," it said.
There are growing concerns over the regime's stability after the execution of Jang Song-Thaek, a senior leader who was also the uncle and former political mentor of North Korean leader Kim Jong-Un.
Seoul and Washington have warned of possible provocative acts by the nuclear-armed North following the purge.
Park called for "watertight security readiness" during her trip Tuesday to a frontline guard post, describing the situation over the border as "ominous".
"We should react sternly and mercilessly to any provocation by North Korea," she said. Sapa-AFP