The South Korean military said it had properly conducted guard operations when a group of four North Koreans crossed the border on a fishing boat near the eastern Gangwon city of Sokcho earlier this week amid criticism over the military's insufficiencies.

At a parliamentary audit on Friday, Kang Shin-chul, head of Joint Chiefs of Staff(JCS) operation headquarters, said the military radar had properly detected the wooden boat at 5:33 a.m. Tuesday, despite the long distance.

Kang said troops then continuously monitored the target, which was one of over one-thousand detected by the radar.

At 6:31 a.m., the military's thermal observation device(TOD) discerned the then-unidentified object, which was followed by further monitoring. At 6:59 a.m., the military discerned that the object could possibly be a vessel, and issued a target number for close verification four minutes later.

The senior official said it is customary for the military to contact the nearest civilian fishing boat for prompt verification when a maritime infiltration is unlikely, and that there was a civilian boat closer to the North Korean boat than the one that first reported the sighting. 

The report was then transferred from municipal authorities to the Navy, after which authorities confirmed that it was of the same vessel under the military's watch and deployed maritime patrol aircraft and a naval vessel.