North Korean leader Kim Jong-un visited an Army unit and urged the military to maintain high combat readiness, its state media reported Wednesday, amid heightened tension on the peninsula following the shocking execution of the leader's uncle.

Kim visited the Command of Large Combined Unit 526 near the western port city of Nampo on Christmas Eve, the day when his late father Kim Jong-il was appointed as supreme commander of the Korean People's Army, the Korean Central News Agency (KCNA) said.

"He instructed the unit to put utmost spurs on rounding off its combat readiness with the firm viewpoint...,always bearing in mind that a war breaks out without any prior notice," the KCNA said in an English dispatch.

The young leader was accompanied by senior officials and military leaders, including Choe Ryong-hae, the chief of the military Politburo, and Ri Yong Gil, the North's military chief, the report said.

Choe has been considered the communist state's new No. 2 man following the recent execution of the current leader's uncle, Jang Song-thaek.

His military inspection coincided with South Korean President Park Geun-hye's first visit to a frontline unit since she came into office in February.

Park ordered service members to deal "sternly and mercilessly" with North Korean provocations to address rising security concerns.

Seoul and Washington have recently stepped up their surveillance on North Korea, as it could resort to provocative moves in an attempt to escalate tensions and divert domestic attention away from the shocking execution of the high-profile politician. (Yonhap News)