North Korea has fired several artillery rounds into the sea near a disputed maritime border with South Korea amid tensions between the two states over a nuclear test conducted by Pyongyang in January.
The South Korean military on Saturday said the rounds had not crossed the border but caused alarm among residents on a nearby island in the South.
Last month North Korea carried out a nuclear test and in February it tested a long-range rocket, which were condemned by South Korea and the United States as grave violations of UN Security Council resolutions.
The allies are expected to begin large-scale annual military drills in early March, which the North calls preparations for war and routinely vows retaliation over.
No unusual movements
Saturday's firing, heard from the island of Baengnyeong, was probably aimed in a northwestern direction from the North's shore as part of an exercise, a South Korean defence ministry official said by telephone, asking not to be named.
The South's office of the Joint Chiefs of Staff later said there were several rounds of artillery fire, revising a comment by the ministry official that there had been a single shot, and there were no other unusual movements by the North's military.
|A South Korean man watches footage of a rocket launch by the North earlier this month [AP/Ahn Young-joon]
South Korea suspended the operation of a jointly run factory park in the North, closing what had been the last window of regular interaction born out of a summit meeting in 2000, when leaders pledged to work for peace and reconciliation.
The area is near the scene of the sinking of a South Korean navy ship in 2010 that the South blames on the North, although Pyongyang denies any role.
The island of Baengnyeong sits just a few miles from the disputed Northern Limit Line (NLL) border and less than 20km at its closest point to the North's shore.