The South Korean Navy returned fire after North Korea shot artillery near the tense western sea border, military officials said Wednesday.

The Navy heard three shots, one of which fell near the Northern Limit Line, and immediately fired back, they said.

No casualties or damage have been reported so far, according to a Seoul official, who added that the government was trying to confirm whether the shots were accidental or deliberate.

The two Koreas, who are technically still at war as their 1950-53 conflict ended in a truce rather than a peace treaty, had a fatal exchange of fire near the maritime border as recently as last November.

The North military bombarded the South Korean island of Yeonpyeongdo near the northwestern sea border in November. Two South Korean civilians and two military personnel were killed.

The Seoul Navy fired three shots toward the border in return to Pyongyang’s firing of three artillery shots around 1 p.m., the Joint Chiefs of Staff said.

“We estimated that one North Korean shell dropped near the NLL,” a JCS official said. “We haven’t noticed any particular movements in the North Korean military but we’re maintaining a defensive posture.”

The official said the North Korean shots appeared to have come from Yongmaedo, about 11 kilometers north of the NLL and some 20km northeast of Yeonpyeongdo. The South’s warnings shots were launched from Yeonpyeongdo.

The NLL, which U.N. forces drew unilaterally at the end of the Korean War, has served as the de facto maritime boundary between the two Koreas.

By Shin Hae-in and news reports (hayney@heraldcorp.com)