North Korea staged an artillery firing drill on Friday near the South Korean border and warned that planned US-South Korean naval exercises at the weekend would bring the peninsula closer to war.
The shelling sent residents of Yeonpyeong island, targeted in a deadly North Korean bombardment on Tuesday, scrambling for air raid shelters, but Seoul said it appeared to be an exercise and that no shells landed on its territory.
The North, unrepentant over its earlier barrage, criticised "the US imperialists and south Korean puppet war-like forces" for what it called an exercise in "sabre-rattling".
"The situation on the Korean peninsula is inching closer to the brink of war due to the reckless plan of those trigger-happy elements to stage again the war exercises targeted against the (North)," its official news agency said.
The latest incident came as Seoul grappled with the domestic political fallout of Tuesday’s attack after the defence minister resigned over criticism that the South’s response to the bombardment had been weak.
A defence ministry spokesman told AFP explosions were heard several times between noon and 3 pm and appeared to have come from the North.
"We assume North Korea carried out firing exercises," he said.