Seoul's Joint Chiefs of Staff said that its overall coastal and maritime defense operations had proceeded "normally," but acknowledged that its radar operation system has "elements that need to be complemented."

"We will maintain a robust vigilance and surveillance posture by crafting supplementary measures," JCS spokesman Col. Kim Jun-rak told reporters during a regular press briefing of the defense ministry.

Some critics argued that maritime border defense appears to have been loosened after the two Koreas set up a buffer zone along the NLL under last year's agreement aimed at reducing tensions and preventing accidental clashes. (Yonhap)