South Korean President Yoon Suk Yeol ordered aides to consider suspending a 2018 inter-Korean military tension reduction agreement if North Korea violates the South's territory again, an official said Wednesday.

Yoon's remark came after five North Korean drones infiltrated South Korean airspace last week, raising serious questions about South Korea's readiness posture, Yonhap News Agency reported.

"President Yoon Suk Yeol instructed the National Security Office to consider suspending the Sept. 19 military agreement in the event North Korea carries out another provocation violating our territory," senior presidential secretary for press affairs Kim Eun-hye told reporters.

Yoon also instructed Defence Minister Lee Jong-sup to establish a joint drone unit tasked with carrying out multiple missions, including surveillance and reconnaissance operations, build a system enabling the mass production of small, hard-to-detect drones within the year and push to develop stealth drones before the end of the year, Kim said.

Yoon's instructions were a call for the South Korean armed forces to build an "overwhelming response capability that goes beyond a proportionate response to North Korea's provocations," Kim explained.

The Sept. 19 agreement, which was signed after a 2018 summit between then President Moon Jae-in and North Korean leader Kim Jong-un, calls for halting all hostile military activity between the Koreas.

It also includes plans to turn the demilitarised zone into a peace zone, devise military guarantees for the activation of cross-border exchanges and establish military confidence-building measures.