President Park Geun-hye said Tuesday that South Korea should deal "sternly and mercilessly" with North Korean provocations as she visited front-line troops amid concerns Pyongyang could attempt provocations following the execution of leader Kim Jong-un's uncle.

"As we all know, the situation and security conditions on the Korean Peninsula are very grave. North Korea's internal situation is ominous and therefore, concerns are growing that the North could attempt provocations," Park said during a visit to an observation post overlooking the border with the North.

"The best way to prevent North Korean provocations is to establish watertight security readiness to make (the North) not dare think of launching provocations. However, if (the North) does launch provocations, we should deal sternly and mercilessly with them," she said.

Park also said she has total trust in the decisions field commanders make.

It was Park's first visit to a military unit since she came into office in February.

The visit came as officials in Seoul have warned that North Korea could resort to provocative moves in an attempt to escalate tensions and divert domestic attention away from the surprise execution of leader Kim's once-powerful uncle, Jang Song-thaek.

On Monday, South Korea's spy agency chief said the North has beefed up artillery units and exercises, and could launch provocations against the South between January and March. He also said Pyongyang is ready to conduct a new nuclear test at any time.

Park first visited a boot camp and watched new conscripts exercise before heading to an observation post overlooking the border with the North and then a general outpost guarding the Demilitarized Zone, a 4-km wide buffer zone separating the two Koreas.

After the execution of Jang, Park has ordered the government to make preparations for all possible contingencies involving North Korea and urged the military to beef up its vigilance, warning that the communist nation could attempt "reckless provocations." (Yonhap News)