One of five North Korean unmanned aerial vehicles that infiltrated South Korean airspace on Dec. 26 was belatedly found to have briefly entered the no-fly zone around the office of President Yoon Suk Yeol in Seoul.

The Joint Chiefs of Staff said on Jan. 5 that an object presumed to be a small enemy drone appears to have flown through a part of the "northern tip" of the 3.7-kilometer radius zone around the presidential office.

The National Intelligence Service said that the drone in question might have taken photos of the presidential office.

Some news media and an opposition party lawmaker suspected a North Korean drone of infiltrating the no-fly zone in Seoul, but the Ministry of National Defense strongly denied such possibility. Defense Minister Lee Jong-sup said in the National Assembly that he was convinced that the drones did not come to Yongsan where the presidential office is located.

It is hard to understand that the military authorities denied strongly despite a reasonable suspicion and even before the final analysis of flight trail of the drone in question. It is also unconvincing that the drone incursion into the no-fly zone was discovered so belatedly. The JCS announcement came 10 days after the incident.

The reversal of position only undermines public trust in the military. Related officials should be held accountable.

When it comes to national security issues including North Korea's military provocation against the South, it is desirable for political parties to speak in one voice.

However, after the military authorities acknowledged the possibility of a North Korean drone entering the no-fly zone, raised by an opposition party lawmaker, the ruling party questioned if the lawmaker had communicated secretly with North Korea but failed to provide grounds for it. There seems to be a gap in its logic. If a map is compared with flight trails of the North Korean drones that the military provided to the National Assembly, one can suspect reasonably that a drone may have passed the no-fly zone.

The opposition party argued the incident exposed the Yoon administration's incompetence and irresponsibility regarding national security. It demanded an immediate dismissal of senior officials in charge of national security and argued a parliamentary probe is needed. This shows the party's intent to politicize the drone incursion.

Rival parties are so occupied with political fight. Now is the time to focus on stronger responses to infiltration by North Korean drones. Political strife in front of an enemy would be self-injury. Probably that is what Pyongyang wants.

The fundamental responsibility lies with North Korea. The South must condemn the North for flying drones into the South Korean airspace.

South and North Korea concluded a military agreement on Sept. 19, 2018 that bans all hostile acts on the ground, on the sea and in the air, but the North has violated the accord 17 times, including shooting at a South Korean guard post over the demilitarized zone and firing artillery shells into inter-Korean maritime buffer zone.

The agreement signed by the Moon Jae-in government has been effectively nullified due to North Korea's violations. When the accord was signed, critics were concerned that it could weaken South Korea's defense by banning military exercises near the military demarcation line and setting up no-fly zone along the line to ban aerial reconnaissance from the zone.

After the drone incursion, President Yoon ordered his aides to consider suspending the military agreement if the North violates the South's territory again. This was an expression of will to deal sternly with North Korea's provocations.

It was a posture the president as the commander-in-chief should take toward the North that does not hesitate to invade the South Korean territory. The presidential office is said to be considering resuming anti-North Korean propaganda using loudspeaker broadcasts and electronic boards in the demilitarized zone and allowing leaflets to be sent toward the North.

It is undeniable that the military's readiness to respond to North Korea's provocation has weakened under the previous administration, which stuck to an appeasement policy toward Pyongyang. The government must find errors and flaws in the military's operational system and set them straight. It ought to go all out to reform the military.