North Korea has fired artillery shots near the disputed sea border with South Korea and the South has returned fire.
The North fired shells into the sea near Baengnyeong Island off the the South's western coast, South Korean news agency Yonhap said.
North Korea said the firing was part of an annual military drill, adding that it would continue.
On Tuesday, North Korea declared a no-sail zone in waters off its coast, media reports say.
South Korea officials said the exchange caused no casualties or damage.
