South Korea has criticised North Korea for an artillery drill near the inter-Korean maritime border.
The shooting practice was a violation of a bilateral military agreement from September 2018, the Defence Ministry said on Monday in Seoul.
North Korea must stop all military activity in the border region, it added.
North Korean state media had previously reported that ruler Kim Jong Un had ordered the shooting during an inspection of a military company on the island of Chagrin in the Yellow Sea.
“The servicepersons of the coastal artillery company fully showed their gun firing skills they cultivated in their day-to-day training to delight the Supreme Leader,” the official KCNA news agency reported.
When the exercises took place was unclear.
A spokesman for the South Korea Defence Ministry confirmed that the shooting exercises were carried out on the island close to the border. He did not name details.
In the course of a rapprochement between the two sides in 2018, the armed forces of both countries had agreed on confidence-building measures close to the heavily militarized border in order to avoid incidents.
However, relations have faltered this year.
Among other things, the leadership in Pyongyang has called on South Korea not to act as an intermediary between North Korea and the U.S.
Recently, North Korea had also significantly upped its criticism of joint manoeuvres between the U.S.and South Korea.
Since a failed summit between Kim Jong Un and U.S. President Donald Trump in Vietnam in February, there has been no progress in negotiations on the North Korean nuclear weapons programme.