South Korea restarted propaganda broadcasts Friday along its border with North Korea, two days after Pyongyang tested a nuclear bomb.

Military tensions are expected to escalate on the peninsula as the North is extremely sensitive to any outside criticism of its leadership and system.

Seoul's move came on the purported birthday of North Korean leader Kim Jong-un, known to be in his early 30s.

The South's military carried out the psychological campaign using loudspeakers for weeks last year in retaliation for the North's land mine attack.

The North described it as an act of war and threatened direct strikes at related facilities.

The crisis ended with the Aug. 25 inter-Korean deal calling for the South to halt the broadcasts in return for some of the North's conciliatory measures, including the reunions of families separated by the 1950-53 Korean War.

At that time, Seoul said it would resume the broadcasts in case of "abnormal" situations.

The broadcasts began to blare sharp criticism of the Kim regime and its human rights abuses, as well as a narrative of South Korea's achievements and even K-pop songs, from 11 locations along the Demilitarized Zone. The messages reach North Korean regions more than 10 kilometers away in daytime and some 24 km at night, according to a defense source.

South Korean officials expect their decision to demonstrate Seoul's resolve to deal sternly with the North's provocation, with the U.N. Security Council planning to impose additional sanctions on it.

Pyongyang has not yet issued any formal response to Seoul's move.

The South's Defense Ministry said it was maintaining the WATCHCON alert at the current level.

The North's military is in a winter training period, and it is strengthening surveillance and its combat posture in some front-line areas, a ministry official said.

If North Korea attacks the loudspeakers, we will immediately retaliate," he said, adding South Korea has deployed K-9 self-propelled artillery and short-range missiles near the loudspeakers. (Yonhap)