An artillery sound was heard near South Korea's frontline Baengnyeong Island Saturday morning and administrative authorities there issued a broadcast to prepare local residents for evacuation.

The county of Ongjin in Incheon Metropolitan City said that the sound of North Korean artillery shots fired was heard at 7:47 a.m. after which the preparatory broadcast was issued.

Earlier, the South Korean military detected a sound in Baengnyeong township presumed to be from the North's coastal artillery.

The military said the North appears to have fired several artillery shells from its coastal base in Jangsan Cape, but the shells are not believed to have crossed the Northern Limit Line(NLL) maritime border.

A South Korean military official said that as no particular moves have been detected from the North's military, the sound is believed to have come from a shooting drill. But the official added that surveillance is being stepped up along the maritime border. 

Meanwhile, if any further situation develops, Ongjin County will immediately issue an announcement to evacuate residents to an air-raid shelter.