The US-led United Nations Command is drawing up a report on a recent border shooting incident between South and North Korea after a field inspection into the southern side of the Demilitarized Zone, officials said Wednesday.

On Sunday, four bullets from North Korea hit a South Korean guard post in the central part of the DMZ in Cheorwon, Gangwon Province, prompting South Korean troops to fire back, according to the Joint Chiefs of Staff.

UNC, which administers the DMZ and enforces the armistice agreement that halted the 1950-53 Korean War, conducted a field investigation on Monday, and has been writing a report of its analysis, military officials said.

The report will focus on whether there were acts that violated the armistice agreement, they added.

"The command could carry out additional investigations into the scene if necessary, and we will continue to fully cooperate with them," an official said.

In a statement sent to Yonhap News Agency, UNC said, "We are currently conducting the investigation but haven't completed it yet. Once completed, we'll provide it to the appropriate authorities and provide what is releasable to the public."

A UNC official said "a full investigation" is under way to look into "multiple parts" of the case. The official also said it could take a couple of days or more to wrap up the investigation, and when the analysis report will be ready depends on the situation.

UNC reportedly failed to carry out a field inspection in the North Korean part of the DMZ.

Asked if the command had contact with the communist country for an explanation, the official simply said UNC has "a couple of ways" of communication with the North Korean side, and all related details will be included in the upcoming report.

The command earlier said it operates a direct communication line with the North Korean military and uses it twice per day for communication checks. Last year, the two sides exchanged over 130 messages using the hotline.

Following the shooting case, South Korea sent a notice to the North and called for an explanation, but has not received a response, according to the defense ministry.

Military sources here said that South Korea fired around 30 rounds of gunshots using K-3 and K-6 machine guns at a North Korean guard post after learning that it was where the gunshots were fired from. Earlier, JCS said the South Korean military fired around 10 shots twice.

North Korea used 14.5-millimeter anti-aircraft machine guns at that time, according to the sources.

Asked about its stance on criticism that it took too long before firing back, the sources said that the response was made "appropriately in accordance with the manual and the judgment of a field commander."

"It took less than 20 minutes from hearing the gunshots to firing back. During that time, we took safety actions for our service personnel, and identified the origin of the gunshots to return fire. I do not think we reacted belatedly," a source said.

Apart from UNC's inspection, the Army's Ground Operation Command launched its own probe into the case to see if there were any issues regarding the military's responses, according to the sources.

Analysis of the North's motives has been under way, but the authorities do not see much indication that the act was an intentional provocation, according to the JCS officials.

US Secretary of State Mike Pompeo also said in an interview with ABC News on Sunday that the US believes the incident was "accidental."

It was the first exchange of gunfire between South and North Korea in years. Under the Comprehensive Military Agreement signed in September 2018, the two Koreas agreed to halt all hostile acts against each other, a move aimed at reducing tensions and building trust.

The DMZ, which is about 250 kilometers long and 4 km wide, is one of the world's most heavily fortified borders and has often been a flashpoint between the rival Koreas, though South Korea has been pushing to turn the zone into a global peace zone. (Yonhap)