South Korean troops are on high alert as a deadline imposed by the North for Seoul to halt loudspeaker propaganda broadcasts on the border draws near.

Pyongyang had previously given the South until Saturday 5:00 p.m. local time (0830 GMT) to turn off the loudspeaker units that have been blasting high-decibel propaganda into the North for the past week.

North Korean has vowed to launch a “very strong military counteraction” if the South Korean government fails to halt broadcasts of anti-Pyongyang propaganda.

The North Korean People’s Army (KPA) said that its frontier soldiers had moved into a “fully armed, wartime state” as ordered by leader Kim Jong-un ahead of the deadline.

The Foreign Ministry in Pyongyang has also said in a statement that the North’s soldiers and people are “poised not to just counter-act or make any retaliation but not to rule out an all-out war to protect the social system, their own choice, at the risk of their lives.”

On Friday, South Korean President Park Geun-hye appeared on television, telling the public and military commanders that what she called further North Korean provocations “will not be tolerated.”

South Korea’s Vice Defense Minister Baek Seung-joo also said that 11 sites with loudspeakers for the anti-Pyongyang broadcasts are likely to be targeted.

Seoul earlier this month turned back on the loudspeakers after it blamed the North for a mine explosion in August that maimed two of its soldiers. Pyongyang, however, denied any role in the assault.

The two Koreas had reached an agreement in 2004 to dismantle their propaganda loudspeakers at the border.

Meanwhile, South Korea blocked access to a tourist observatory close to the border with North Korea.

The Dora Observatory looking across the Demilitarized Zone, an area between the two Koreas established in the 1950s, was also shut down by soldiers from the South.

The Korean Peninsula has witnessed a new rise in tensions after the South on Thursday fired shells into the North after a rocket attack by Pyongyang.

The two Koreas remain technically at war after the 1950-53 Korean War ended in an armistice, not a peace treaty.