US Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey and his South Korean counterpart Adm. Choi Yoon-hee have agreed to respond to any further provocations by North Korea with counterattacks, the Yonhap News Agency reports.

TOKYO (Sputnik) – An official from South Korea’s Joint Chiefs of Staff told the South Korean news agency that the two military chiefs held a phone conversation on Saturday, resolving "to deter North Korea from launching additional threats."

Earlier, Yonhap reported citing unanimous sources that North Korea had started deploying artillery in the demilitarized zone.

On Thursday, North Korea reportedly fired shells at a South Korean military base across the demilitarized zone. Seoul retaliated with dozens of heavy artillery rounds.

Pyongyang's Deputy UN Ambassador An Myong Hun stressed on Friday that North Korea did not fire a single shell or bullet on August 20.

The Thursday incident, which was the first major armed confrontation between the neighbors in five years, came in the wake of Seoul’s resumed broadcasting of military propaganda over the border toward North Korea, a practice it had suspended over a decade earlier.

#SouthKorea on top alert as North Korea's attack deadline looms http://t.co/3bMWC0n0px pic.twitter.com/oX4sbMqFDh — The Straits Times (@STcom) August 22, 2015

The North Korean People's Army had warned that it would destroy the South Korean loudspeaker systems located near the demilitarized zone, if Seoul continued to operate them.

Under the North Korean ultimatum, Saturday is the last day for Seoul to terminate its broadcasting.

On Friday, North Korea called on the UN Security Council to hold an urgent meeting on the situation on the Korean peninsula, accusing South Korea and the United States of laying false blames on Pyongyang.

Earlier in the day, North Korea’s leader Kim Jong Un ordered the country’s army to bring the frontline combined units to full combat readiness.

South and North Korea are still formally at war, as no peace treaty was ever signed after the Korean War of 1950-1953.