Kim Min-seok, a ministry spokesman, said the expectation was based on observation of recent exercises conducted by Pyongyang, Yonhap news agency reported.
Unusual levels of participation by the North's artillery, special forces and air force were seen over the winter months, Kim said.
The North has "tended to provoke" South Korea whenever there was a change of political power in Seoul, he said.
South Korea has increased surveillance of the North to guard against a sudden attack, the spokesman added.
Joint maneuvers between South Korea and the United States begin Friday and will run through April 30. While Seoul and Washington said the exercise is strictly defensive, Pyongyang claims the maneuvers are intended to attack the North.