South Korean Defence Minister Han Min-koo vows that Seoul will punish North Korea if it carries out additional attacks.
"As a minister who is responsible for the national defence, this time, I will make sure to sever the vicious cycle of North Korea's provocations while keeping our people's safety as a priority."
South Korea said its military on Thursday fired dozens of shells toward North Korea, which Seoul said had earlier launched artillery shells twice into the south side in the western border. However, the North Korean side has strongly denied the accusation.
According to South Korean officials, 11 sites with loudspeakers broadcasting anti-Pyongyang messages near the border are likely to be the targets.
North Korea leader Kim Jong Un has put his country's troops in a fully armed state of war on Friday.
North Korea's state run television KRT says the North is prepared for military action if Seoul did not meet the Saturday deadline to cease the broadcasts.
"General Staff of Korean People's Army on Thursday sent an ultimatum to the South Korean Defence Ministry that the KPA would launch a strong military action unless South Korea stops broadcasting towards the North. It must also dismantle its psychological warfare system on the border within 48 hours."
No causalities have been reported from the exchange of fire.
As a response, UN Secretary-General Ban Ki-moon has urged the parties to refrain from taking any further measures that might increase tensions.
On Friday, Chinese Foreign Ministry spokeswoman Hua Chunying also called for relevant parties to stay calm and deal with the situation through contact and dialogue.
At the same time, US Assistant Secretary of Defence for Asian and Pacific Security Affairs David Shear has expressed concerns over the latest tensions.
"The United States remains steadfast in its commitment to the defence of its allies, and will continue to coordinate closely with the Republic of Korea. The DPRK's provocative actions heighten tensions, and we call on Pyongyang to refrain from actions and rhetoric that threaten regional peace and stability, and we are at one with our ROK ally on this."
It is also being reported that US has resumed its annual military exercise with South Korea after a temporary halt to coordinate over South Korea's shelling with the north.
Earlier this month, South Korea resumed blaring anti-north propaganda messages through 11 loudspeakers, after accusing Pyongyang of planting landmines that wounded two South Korean soldiers.
For CRI, I am Wang Mengzhen.
