"Since North Korea can carry out provocations at any time, we are constantly on alert and ready to respond immediately," the official said on condition of anonymity.
"We are closely monitoring any movement in the North's military, under the assumption that the North can destabilize the conditions on the Korean Peninsula with a major provocation even during Chuseok, which is one of our biggest traditional holidays," he added.
There are worries that the North could carry out additional provocations on and around Oct. 10, the 72nd founding anniversary of the ruling Workers' Party of Korea.
Earlier, the presidential office Cheong Wa Dae raised the possibility of a development taking place around the upcoming anniversary.
Tensions have spiked since the North conducted its sixth and most powerful nuclear detonation test early this month.
Concerns over a possible military conflict have flared up as the leaders of the United States and the North exchanged bellicose rhetoric each threatening the other with tough military action.
The Chuseok or autumn harvest celebration, falls on Wednesday this year, but most people get 10 days off from Saturday through Oct. 10, as there are two weekends and national holidays preceding and following Chuseok, source from the Yonhap.